The history of the steam-engine is a subject on which so much has been written in books and magazines now before the public, that what I am about to offer, though pretending nothing new, yet I hope may be looked upon as containing something useful as well as instructive, both to the practical and the amateur mechanic. I shall therefore, in as small a compass as possible, trace the steam-engine from its first and early stages up to its present perfect state as our grand motive power. The first mention made of the vapour of water, as formed by the action of heat upon it, is found to be as far back as 120 B.C., when one Hero of Alexandria employed this vapour for the purpose of driving a machine. It is a well-known fact that when water is brought up to a certain degree of heat, called the boiling-point, that it sends forth a vapour, the elastic properties of which, when in an open vessel, are not perceived—as, for instance, in a common pan—yet if the vessel is closed or shut up at the top, you will find that the vapour acquires such a degree of elastic force, that, if not allowed to escape by fair means, it would soon make a way or vent for itself by bursting whatever vessel it was contained in. Steam is thus highly elastic, but when separated from the fluid out of which it is generated, it does not possess a greater elastic force than the same quantity of air. If, for example, a vessel is filled with steam only at 212 deg., it may be brought to a red heat without fear of bursting; but if water is also in the vessel, each additional quantity of heat causes a fresh quantity of steam to be generated, which adds its elastic force to that of the steam already in the vessel, till the constantly accumulating force at last bursts the vessel.

This elastic vapour is called steam, and it is by this that that most beautiful machine, the steam-engine, is driven. As you all know, by this vapour or air—for it is invisible till it loses part of its heat—enormous power is obtained in a small compass, and the labour of man reduced to nothing compared with former ages. Many men laboured to perfect machinery to be worked by this vapour of water, and many came near the mark; but it remained for the great Watt, at the Soho Works, Birmingham, to bring the engine to its useful and working state, for though discovered as a motive power 120 B.C., it was yet reserved for this truly great man to be what may be termed the inventor of the steam-engine.

In 120 B.C., Hero of Alexandria made a machine to be driven by steam. It consisted of a hollow sphere into which the steam was admitted; projecting from the sphere were two arms, from which the steam escaped by three holes on the side of each arm opposite to that of the direction of its revolution, which, by removing the power from off the one part of each arm, caused it to revolve in the direction opposite to that of the hole that allowed the steam to escape. This kind of engine has been for some years in use by Mr. Ruthven of Edinburgh. There are others who have followed very closely on Hero's plan in more ways than one; for instance, it is the common Barker's mill, though with this difference, that his mill is driven by water instead of steam: Avery, also, made a steam-engine almost exactly the same. I may here, perhaps, just be allowed to mention what a little water and coal will produce, as it will show at once from whence our power is derived. "A pint of water may be evaporated by two ounces of coal; in its evaporation it swells to 216 gallons of steam, with a mechanical force equal to raising a weight of thirty-seven tons one foot high." A pound of coal in a locomotive will evaporate about five pints of water, and in their evaporation these will exert a force equal to drawing two tons on a railway a distance of one mile in two minutes. A train of eighty tons weight will take 240 passengers and luggage from Liverpool to Birmingham and back, each journey about four and a quarter hours; this double journey of 190 miles being effected by the combustion of one and a half tons of coke, worth about twenty-four shillings. To perform the same work by common road would require twenty coaches, and an establishment of 3800 horses, with which the journey would be performed each way in about twelve hours, stoppages included. So much for the advantages of steam.

The Romans are supposed to have had some knowledge of the power of steam. Among amusing anecdotes, showing the knowledge the ancients had of steam, it is told that Anthemius, the architect of Saint Sophia, lived next door to Zeno. There existed a feud between them, and to annoy his neighbour, Anthemius had some boilers placed in his house containing water, with a flexible tube which he could pass through a hole in the wall under the floor of Zeno's dwelling; he then lit a fire, which soon caused steam to pass through the tube in such a quantity as to make the floors to heave as if by an earthquake. But to return. We next come to Blasco de Garay (A.D. 1543), who proposed to propel a ship by the power of steam. So much cold water seems to have been thrown on his engine, that it must have condensed all his steam, as little notice is taken of it except that he got no encouragement. We find that it has also been used by some of the ancients in connection with their deities. Rusterich, one of the Teutonic gods, which was found in an excavation, proves how the priests deceived the people. The head of this one was made of metal and contained a pot of water. The mouth and another hole in the forehead being stopped by wooden plugs, a fire of charcoal was lighted under this pot of water, and at length the steam drove out the plugs with a great noise, and the god was shrouded in a mist of steam which concealed him from his astonished worshippers.

In 1629, Giovanni Branca of Loretto in Italy, an engineer and architect, proposed to work mills and other machinery by steam blowing against vanes, much in the same way as water does in turning a wheel. The waste of steam in such a plan is so obvious, that it is not to be wondered at that it did not produce any great results, as we all know that the moment we let steam out of his case, the case is all up with him, and he dies a natural death. He is a most delicate yet powerful agent, and requires to be kept warm in all weathers—this fact does not seem to have struck Mons. Branca when he let him out of his boiler.

The next person we come to, and perhaps the first of any note, is the Marquis of Worcester in 1663 (died 1667). He was a man who seems, as far as history tells us, to have taken a great interest in furthering the advancement of steam. He was not contented with one invention, but published a book entitled "A Century of Inventions," and in this work he describes a means of raising water by the pressure of steam. The Marquis appears to have been a politician as well as an inventor, as we find he was engaged on the side of the Royalists in the Civil Wars of the Revolution, lost his fortune and went to Ireland, where he was imprisoned. Escaping to France, from thence he returned to London as a secret agent of Charles II., but was detected and imprisoned in the Tower, where he remained till the Restoration, when he was set at liberty. One day, while in prison, he observed the lid of the pot in which his dinner was being prepared lifted up by the vapour of the water boiling inside. Reflecting on this, he turned his mind to the matter, and thought that this vapour, if rightly applied, might be made a useful moving power. He thus describes his invention in his 68th Article: "I have contrived an admirable way to drive up water by fire, not by drawing or sucking it upwards, thirty-two feet. But this way hath no bounds, if the vessels be strong enough." He then goes on to say, that "having a way to make his vessels, so that they are strengthened by the force within, I have seen the water run like a constant stream forty feet high. One vessel rarified by fire driveth forty of cold water, and one being consumed, another begins to force, and refill with cold water, and so on successively, the fire being kept constant. The engineman having only to turn two cocks, so as to connect the steam with the one or the other vessel."

In this engine, if it can be called an engine, we see that the Marquis had a good idea of the power of steam, but he had none, you will observe, as to the action of the condensation which would immediately take place when the steam from the boiler was brought into contact with the cold water to be raised. Therefore this plan would be most expensive, on account of the great loss of steam by condensation. It was, however, quite able to produce the effect, though only equal to raising 20 cubic feet of water, or 1250 lbs., one foot high by one pound of coal, or about the two-hundredth part of the effect of a good steam-engine. After this, of course, it proved of no avail; but still we may say that the Marquis of Worcester was among the first who tried to make, and did do so, steam a moving power.

Our next is Denys Papin (died 1710), a native of Blois, in France, who was mathematical professor at Marpurg. To him is due the discovery of one of the qualities of steam—its condensation, so as to produce a vacuum, to the proper management of which our modern engines owe much of their efficacy. Papin seems to have been the first who conserved the idea of the cylinder and piston, which he made to act on atmospheric principles—that is to say, he took a cylinder with a piston moving up and down in it, and found that by removing the air from under the piston in the cylinder, that the pressure of the atmosphere would drive it down to the bottom of the cylinder: this he performed by admitting steam, and then condensing it rapidly, so causing the required vacuum. The pressure of the atmosphere is as near as may be 16 lbs. on every square inch of surface on the globe: this is obviously the weight of the columns of air extending from that square inch of surface upwards to the top of the atmosphere. This force is thus measured: Take a glass tube 32 inches long, open at one end and closed at the other; provide also a basin full of mercury; let the tube be filled with mercury and inverted into the basin. The mercury will then fall in the tube, till it gets to that height which the atmosphere will sustain. This is nothing more than the barometer used in all our houses. If the action of the tube be equal to a square inch, the weight of the column of mercury in the tube would be exactly equal to the weight of the atmosphere on each square inch of surface. Thus Papin discovered a great step in the steam-engine, though it was not much acted on for some years; he was also the first who proposed to drive ships with paddles worked by steam.

We now come to Thomas Savory, who got a patent in 1698 for a method of condensing steam to form a vacuum. Savory describes his discovery in this way:—Having drank a flask of wine at a tavern, he flung the empty flask on the fire, and then called for a basin of water to wash his hands. A little wine remained in the flask, which of course soon boiled, and it occurred to him to try what effect would be produced by putting the mouth of the flask into the cold water. He did this, and in a moment the cold water rushed up and filled the flask, this being caused by the steam being condensed and leaving a vacuum, which Nature abhors, and rather than permit this the water rushed up and took the place formerly occupied by the now condensed steam. We see by this in how simple a way great ends are produced, and in the age in which this happened, the result may be indeed be said to have produced a great end. The engine of Savory was used for some years as a machine to raise water. The principle of his engine was just as I have stated, and consisted of two cases and other various parts, and this engine possessed advantages over that of the Marquis of Worcester in sucking up the water as well as forcing.

Savory's engine consisted of two steam vessels connected to a boiler by tubes; a suction pipe, or that pipe which leads from a pump of the present day to the well, and communicating with each of the steam vessels by valves opening upwards; a pipe going from these steam vessels to any required height to which the water is to be raised. The steam vessels were connected to this pipe by other valves, also opening upwards, and by pipes. Over the steam vessels was placed a cistern, which was kept filled with cold water. From this proceeded a pipe with a stopcock. This cistern was termed the condensing cistern, and the pipe could be brought over each steam vessel alternately from the boiler. Now, suppose the tubes to be filled with common air, and the regulator placed so that one tube and the boiler are made to communicate, and the other tube and the boiler closed, steam will fill one of the steam vessels through one tube; at first it will condense quickly, but erelong the heat of the steam will impart its heat to the metal of the vessel, and it will cease to condense. Mixed with the heated air, it will acquire a greater force than the air outside the valve, which it will force open, and drive out the mixture of air and steam, till all the air will have passed from the vessel, and nothing but the vapour of water remain. This done, a cock is opened, and the water from the cistern is allowed to flow over the outside of the steam vessel, first having stopped the further supply of steam from it; this produced the immediate condensation of the steam contained in it, by the temperature being brought down again by the cold water, and the condensation thus produced caused a vacuum inside the vessel. The valve will then be kept closed by the atmosphere outside, and the pressure of the air on the surface of the water in the well or reservoir will open another valve, force the water up the pipe, till, after one or two exhaustions—if I may so term it—it will at last reach the second vessel. Thus far the atmosphere has done all the work, but at last the water fills the vessel, and then comes the forcing point. Now the power of the steam itself is used to drive the water up the pipe. The steam is again let into the vessel, now filled in whole, or at least in great part, with water; at first it will, as before, condense rapidly, but soon the surface of the water will get heated, and as hot water is lighter than cold, it will keep on the surface, and the pressure of the steam from the boiler will drive all the water from the vessel up the pipe. When it is empty the cock is again opened, and the steam, which the vessel by this time only contains, is again condensed, and the same process which I have just described is again commenced and carried out, thus making Savory's engine a complete pump by the aid of the vapour of water as raised by fire.

Savory had the honour of showing this engine to His Majesty William III. at Hampton Court Palace, and to the Royal Society. He proposed the following uses, which perhaps may as well be mentioned, as they show how little was then known of the real value of the power of steam:—1. To raise water to drive mill-wheels—fancy erecting a steam engine now, of say fifty horse-power, to raise water to turn a wheel of say thirty; 2. To supply palaces and houses with water; 3. Towns with water; 4. Draining marshes; 5. Ships; 6. Draining mines. There is one more thing I may mention as curious, that though the steam he used must have been of a high pressure, he did not use a safety-valve, though it had been invented about the year 1681 by Papin. The consumption of fuel was enormous in Savory's engine, as may easily be perceived from the great loss of steam by condensation. Nevertheless, it was on the whole a good and a workable engine, as we find the following said of it by Mr. Farey:—"When comparison is made between Captain Savory's engine and those of his predecessors, the result will be favourable to him as an inventor and practical engineer. All the details of his invention are made out in a masterly style, so as to make it a real workable engine. His predecessors, the Marquis of Worcester, Sir S. Morland, Papin, and others, only produced outlines which required to be filled up to make them workable."

I must not detain you much longer before I proceed to the great Watt, but I will just name Newcomen, who invented an engine with a cylinder, and introduced a beam, to the other end of which he fixed a pump rod like a common or garden pump. He made the weight of the pump and beam to lift the piston, and then let the steam enter below the piston and condensed it by a jet of water, thus causing a vacuum, when the pressure of the atmosphere drove the piston from the top to the bottom of the cylinder and lifted the pump rods in the usual way. There were various cocks to be opened and shut in the working of this engine for the right admission of steam and water at the required moments, a task which was performed by boys who were termed cock-boys. I will now mention an instance which, though in practice not to be imitated, yet was one of those happy accidents which sometimes turn out for the best. One of these boys, like many, more fond of play than work, got tired of turning these cocks day by day, and conceived the idea of making the engine do it for itself. This idle boy—we will not call him good-for-nothing, as he proved good for a great deal in one way—was named Humphrey Potter, and one day he fixed strings to the beam, which opened and shut the valves, and so allowed him to play, little thinking this was one of the greatest boons he could possibly have bestowed on the world at large, for by so doing he rendered the steam-engine a self-acting machine.

We now come to a period which was destined to advance the cause of steam to a far greater extent—in fact, the time which rendered the steam-engine the useful and valuable machine it now is. This is the time of James Watt. This great man, be it said to the credit of Scotland, was born in Greenock, on the Clyde, on the 19th January 1736. His grandfather was a farmer in Aberdeenshire, and was killed in one of the battles of Montrose. His father was a teacher of mathematics, and was latterly chief magistrate of Greenock. James Watt, the celebrated man of whom I now speak, was a very delicate boy, so much so, that he had to leave school on account of his health, and was allowed to amuse himself as he liked. This he did in a scientific way, however, as an aunt of his said to him one day: "Do you know what you have been doing? You have taken off and put on the lid of the teapot repeatedly; you have been holding spoons and saucers over the steam, and trying to catch the drops of water formed on them by it. Is it not a shame so to waste your time?" Mrs. Muirhead, his aunt, was little aware that this was the first experiment in the way which afterwards immortalised her nephew.

In 1775 Watt was sent to London to a mathematical instrument maker, but could not stay on account of his health, and soon afterwards came back to Glasgow. He then got rooms in the College, and was made mathematical instrument maker to the University, and he afterwards opened a shop in the town. He was but twenty-one years of age when he was appointed to this post in the College, and his shop became the lounge of the clever and the scientific. The first time that his attention was directed to the agency of steam as a power was in 1734, when a friend of his, Mr. Robinson, who had some idea of steam carriages, consulted him on the subject,—little is said of this, however. In 1762 Watt tried some experiments on high-pressure steam, and made a model to show how motion could be obtained from that power; but did not pursue his experiments on account of the supposed danger of such pressure. He next had a model of Newcomen's engine, which would not work well, sent him to repair. Watt soon found out its faults, and made it work as it should do. This did not satisfy him, and setting his active mind to work, he found in the model that the steam which raised the piston had of course to be got rid of. This, as a natural consequence, caused great loss of heat, as the cylinder had to be cooled so as to condense the steam; and this led him at last, after various plans, to adopt a separate vessel to condense this steam. Of course, if you wish to save fuel, it is necessary that the steam should enter a heated cylinder or other vessel, or else all the steam is lost,—or in other words, condensed,—that enters it, until it has from its own heat imparted so much to the cylinder as to raise it to its own temperature, when it will no longer condense, and not till then does it begin to exert its elastic power to produce motion. This was the great object gained by James Watt, when, after various experiments, he gave up the idea altogether of condensing steam in its own or working cylinder, and then made use of a separate vessel, now called the condenser.

The weight of steam is about 1800 times less than water. I may here perhaps mention also that water will boil at 100 degrees Fahr. in vacuo, whereas in atmosphere it takes 212 degrees to boil. There is also a thing perhaps worth knowing to all who wish to get the most stock out of bones, &c., that if they are boiled in a closed vessel, that is to say, under a pressure of steam, a very large increase in quantity of the stock will be produced, because the heat is increased. A cubic inch of water, evaporated under ordinary atmospheric pressure, will be converted into a cubic foot of steam; and a cubic inch of water, evaporated as above, gives a mechanical force equal to raising about a ton a foot high.

The next great improvement of Watt, in addition to the condenser, is the air-pump, the use and absolute necessity for which you will understand when I explain its action. Watt first used it for his atmospheric engine. The piston of this engine was kept tight by a flow of oil and water on the top, which tended to make the whole a troublesome and bad-working machine. The cold atmosphere, as the piston went down, of course followed it and cooled the cylinder. On the piston again rising, some steam would of course be condensed and cause waste. If the engine-room could be kept at the heat of boiling water, this would not have been the case, but the engineman who could live in this heat would also require to be invented, and so this had to be given up. Watt's next and most important step was the one which brings us to talk of the steam-engine as it now is in the present day. This important step was the idea, of making the steam draw down the piston, as well as help to drive it up; in the first engines it was raised by the beam, and steam used only to cause a vacuum, so as to let the air drive it down. All before this had been merely steps in advance, like those of children, who must walk before they can run; so was it with the steam-engine. It was uphill work for many years, and the top of the hill cannot be said to have been readied till Watt worked out this grand idea. The first engine could only be called atmospheric; now it was destined to become in reality a steam-engine. Time would fail were I to attempt to go into any details of all the experiments through which Watt toiled to bring his ideas to perfection—enough to say that he did so; and I trust you will be able, through the description I will endeavour to give, to understand how well his labour was bestowed, and how beautiful the result has proved for the benefit of the world at large. In 1773, Watt removed to Soho, near Birmingham, where a part of the works was allotted to him to erect the machinery necessary to carry out his inventions on a grand scale.

We must now proceed to some of the useful points of the engine, all I have before mentioned simply relating to the inventors and improvers; but having brought it so far, I may now, I think, proceed further. The first use of the steam-engine was simply to raise water from mines, and for long it was thought it could be used for nothing else; so much so, that it was at one time used to raise water to turn wheels and thus produce motion. One of its first uses after it became a really useful machine was to propel ships, though many a weary hour was spent to bring it to this point. There is a very pretty monument on the Clyde, dedicated to Mr. Bell, who I believe was the first person who successfully brought steamers to work on its waters. The first who used steam for ships was Mr. James Taylor, in conjunction with Mr. Miller of Dalswinton. The danger of the fire-ship took such hold on people's minds that it was with great toil and difficulty they were persuaded to venture on the face of the waters in such dangerous and unseamanlike craft. But go to Glasgow Bridge any day, and you will see how time has overcome fear and prejudice, for our ocean is covered with steamers of all sizes. It is not many years ago since it was said that steamers could never reach America; this has given way to proof, and even Australia has been reached by steam. I know of a steamer building which could carry the whole population of this place and not be full; she is 680 feet or 226 yards long, and a large vessel would hang like a boat alongside her.

The first attempt at giving motion by steam to ships was of course only in one way—by a ratchet at the end of a beam, at one moment driving and the next standing still. This was on account of the engine being only in power one half of the stroke; but by the double-acting engine being introduced, and the steam acting both ways, it became at last a steady mover (without the aid of two or three cylinders, as in the first engines, one to take up the other as the power was given off), by a ratchet on the end of a beam or else a chain. This acted on the shaft which moved the paddles. It is to Watt that we are indebted for the crank and direct action, so as to give a circular motion to the wheels.

We find in 1752 a Mr. Champion of Bristol applied the atmospheric engine to raise water to drive a number of wheels for working machinery in a brasswork, in other words, a foundry. Also, in Colebrokedale, steam-engines were used to raise water that had passed over the wheel, so as to save water. All these plans have, however, now passed by, like the water over the wheel, and we now have the engine the prime mover—the double action of the steam on the piston, this acting on the sway beam, and the beam on the crank, which, by the assistance of the fly-wheel on land or fixed engines, gives a uniform motion to the machine. All these have now enabled us to apply the engine as our grand moving power. One great and important point in the engine is the governor, and the first modes of changing the steam from the top to the bottom of the cylinder were cumbrous, till the excentric wheel was devised.

Boilers also have to be attended to—these were at first rude and now would be useless. They were unprovided with valves, gauge-cocks, or any other safety, all of which are now so well understood that nothing but carelessness can cause a blow-up. One of the greatest causes of danger is that of letting there be too little water in the boiler, and thus allowing it to get red-hot, when, if you let in water, such a volume of steam is generated that no valve will let it escape fast enough. Force or feed pumps are also required to keep the water in the boiler at a proper height, which is ascertained by the gauge-cocks. Mercury gauges for low pressure act according to the pressure of the atmosphere; high-pressure boilers of course require a different construction, as the steam is greater in pressure than the air.

Having got so far in my subject, I think before concluding I must devote a short time in showing the first steps of the locomotive; the more so, as I am speaking to those who are so largely engaged in the daily working of that now beautifully perfect machine. Various and for a time unsuccessful experiments were made to bring out a machinery or travelling engine, as it was first called. A patent was taken by a Mr. Trevethick for a locomotive to run on common roads, and to a certain extent it did work. An amusing anecdote is told of it. In coming up to a toll-gate, the gatekeeper, almost frightened out of his seven senses, opened the gate wide for the monster, as he thought, and on being asked what was to pay, said "Na-na-na-na!" "What have we got to pay?" was again asked. "No-noth-nothing to pay, my dear Mr. Devil; do drive on as fast as you can!" This, one of the first steam carriages, reached London in safety, and was exhibited in the square where the large station of the London and North-Western Railway now stands. Sir Humphrey Davy took great interest in it, and, in writing to a friend, said: "I shall hope soon to see English roads the haunts of Captain Trevethick's dragons." The badness of roads, however, prevented its coming into general use.

Trevethick in 1804 constructed a locomotive for the Merthyr and Tydvil Rail in South Wales, which succeeded in drawing ten tons at five miles an hour. The boiler was of cast-iron, with a one-cylinder engine, spur gear and a fly-wheel on one side. He sent the waste steam into the chimney, and by this means was very nearly arriving at the blast-pipe, afterwards the great and important discovery of George Stephenson. The jumping motion on the bad roads, however, caused it constantly to be dismounted, and it was given up as a practical failure, being sent to work a large pump at a mine. Trevethick was satisfied with a few experiments, and then gave it up for what he thought more profitable speculations, and no further advances were made in locomotives for some years. An imaginary difficulty seems to have been among the obstacles to its progress. This was the supposition that if a heavy weight were to be drawn, the grip or bite of the wheels would not be sufficient, but that they would turn round and leave the engines stationary, hence Trevethick made his wheels with cogs, which of course tended to cause great jolts, as well as being destructive to the cast-iron rails.

A Mr. Blenkinsop of Leeds patented in 1811 a locomotive with a racked or toothed rail. It was supported on four wheels, but they did not drive the engine; its two cylinders were connected to one wheel behind, which was toothed and worked in the cog-rail, and so drove the engine. It began running on Middleton Coal Rail to Leeds, three and a quarter miles, on the 12th August 1812, and continued a great curiosity to strangers for some years. In 1816 the Grand Duke Nicholas of Russia saw this engine working with great interest and expressions of no slight admiration. An engine then took thirty coal-waggons at three and a quarter miles in an hour.

We next come to Messrs. Chapman of Newcastle, who in 1812 tried to overcome the supposed want of adhesion by a chain fixed at the ends of the line and wound round a grooved drum driven by the engine. It was tried on the Heaton Rail near Newcastle, but was found to be so clumsy that it was soon abandoned. The next was a remarkable contrivance—a mechanical traveller to go on legs. It never got beyond its experimental state, and unfortunately blew up, killing several people. All these plans show how lively an interest was then being taken in endeavouring to bring out a good working locomotive. Mr. Blackett, however, persevered hard to perfect a railway system, and to work it by locomotives. The Wylam waggon-way, one of the oldest in the North, was made of wooden rails down to 1807, and went to the shipping-place for coals on the Tyne. Each chaldron-waggon was originally drawn by a horse with a man in charge, only making two journeys in the one day and three on the following, the man being allowed sevenpence for each journey. This primitive railway passed before the cottage where George Stephenson was born, and was consequently one of the first sights his infant eyes beheld; and little did his parents think what their child was destined to work out in his day for the advancement of railways. Mr. Blackett took up the wood and laid an iron plate-way in 1808, and in 1812 he ordered an engine on Trevetbick's principle. It was a very awkward one, had only one cylinder of six inches diameter, with a fly-wheel; the boiler was cast-iron, and was described by the man who had charge of it as having lots of pumps, cog-wheels, and plugs. It was placed on a wooden frame with four wheels, and had a barrel of water on another carriage to serve as a tender. It was at last got on the road, but would not move an inch, and her driver says:—"She flew all to pieces, and it was the biggest wonder we were not all blown up." Mr. Blackett persevered, and had another engine, which did its work much better, though it often broke down, till at length the workmen declared it a perfect plague. A good story is told of this engine by a traveller, who, not knowing of its existence, said, after an encounter with the Newcastle monster working its great piston, like a huge arm, up and down, and throwing out smoke and fire, that he had just "encountered a terrible deevil on the Hight Street road."

We now come to George Stephenson, who did for the locomotive what Watt did for our other steam-engines. His first engine had two vertical cylinders of eight inches diameter and two-feet stroke, working by cross-heads; the power was given off by spur-wheels; it had no springs, consequently it jolted very much on the then bad railways; the wheels were all smooth, as Stephenson was sure the adhesion would be sufficient. It began work on the 25th July 1814, went up a gradient of one in 450, and took eight waggons with 30 tons at four miles an hour. It was by far the most successful engine that had yet been made. The next and most valuable improvement of Stephenson was the blast-pipe—by its means the slow combustion of the fire was at once overcome, and steam obtained to any amount. This pipe was the result of careful observation and great thought. His next engine had horizontal connecting rods, and was the type of the present perfect machine. This truly great man did not rest here, but time would fail, as well as your patience, if I were to proceed further. Enough to say, that he afterwards established a manufactory at Newcastle, and time has shown the result and benefit it has proved to the whole world at large. A short time before the Liverpool and Manchester Railway was opened, Stephenson was laughed at because he said he thought he could go thirty miles an hour, and was urged before the House of Commons not to say so, as he might be thought to be mad. This I have from person who knew the circumstances. Nevertheless, at the trial, I believe the "Rocket" did go at the rate of thirty miles an hour, to the not small astonishment of the world, and especially to the unbelievers in steam as a land agent. The stipulation made was that trains were to be conveyed at the rate of twelve miles an hour.

In our present perfect engines, the coke or fuel consumed per mile is about 18 lbs. with a train of 100 tons gross weight, carrying 250 passengers. A first-class carriage weighs 6 tons 10 cwts.; a second-class, 5 tons 10 cwts., each with passengers; a Pullman car weighs about 30 tons. Our steamers consume 5 lbs. of coal per horse-power in one hour. And last, not least, one of the greatest improvements we have had in steam propulsion is the screw. Again, I may also name the great advantage derived from steam by our farmers in thrashing out grain. The engines principally used in farm-work are what are termed high-pressure, or of the same class as the locomotive. The great saving in cost in the first place, the simplicity and ease of action in the second, and the small quantity of water required to keep them in action, are all reasons why they should be preferred. The danger in the one, that is, the high-pressure, over the condenser, is very small, and all that is required is common care to guard against accidents. Steam being a steady power, is much to be preferred to water, as by its constant and uniform action the tear and wear of machinery is much diminished, and of course proportionate saving made in keeping up the mill or any other machinery.

Having now, to the best of my power, so far as a single lecture will permit, brought the steam-engine from 120 B.C. to the present time, it only remains for me to say, that it shows how actively the mind of man has been permitted to work to bring it to perfection by the direction of an all-wise Providence, "who knows our necessities before we ask, and our ignorance in asking." A traveller by rail sees but little of the vast and difficult character of the works over which he is carried with such ease and comfort. Time is his great object. No age of the world has conquered such difficulties as our engineers have had to deal with, and the result is now before the eye of every thinking traveller. Our engineers were at first self-taught, and many a self-taught man has had reason to rejoice in the time he spent in his education. Of these men we have examples in Brindley, who was at first a labourer and afterwards a millwright; Telford was a stone-mason; Rennie a farmer's son apprenticed to a millwright; and George Stephenson was a brakesman at a colliery. Perseverance with genius, and a determination to overcome, made them the great men they were. That you may so persevere and strive is the earnest wish of him who has this evening had the great pleasure of giving you this lecture, and who feels so greatly obliged to you for the very patient hearing you have given him.



ON ATTRACTION.[B]

Gravitation.—Attraction, which may be illustrated by the effect a magnet has on a piece of iron, may be viewed generally as an influence which two bodies, say, exert on each other, under which, though at a distance, they tend to move towards each other till they come into contact. The force by which a body has weight, and, when free, falls to the ground, is of this nature; and it is called, from gravis, "heavy," the gravitating force of the earth, because it causes weight, and because, though emanating in a small degree from the falling body, it is mainly exerted by the earth itself. It is under the action of gravity that a pendulum oscillates: it is by that unseen influence it begins to sway alternately downward and upward as soon as it is moved to a side; and it is only because it is withheld by the rod that the ball or bob keeps traversing the arc of a circle and does not fall straight to the earth.

All material substances, however small, and however light, buoyant, and ethereal they may seem, are subject to this force: the tiniest speck in a sunbeam and the most volatile vapour, equally with the heaviest metal and the hugest block, the particles of bodies as well as the bodies themselves. The rising of a balloon in the air may seem an exception to this law; but it is not so; for the balloon rises, not because the particles of the gas with which it is inflated are not acted upon by the earth's attraction, but because the air outside being bulk for bulk heavier than the air inside, its particles press in below the balloon and buoy it up, until it reaches a stratum of the atmosphere where, the pressure being less, the air outside is no heavier than the air within—a fact which rather proves than disproves the universal action of gravitation; because the greater weight of the air in the lower strata of the atmosphere is due to the pressure of the air in those above, and the balloon ceases to ascend because it has reached a point where the air outside is the same weight as the air within, and the weight in both cases is caused by the attraction of the earth.

And not only is the force of attraction universal, it is the same for every particle; for though this may seem to be contradicted by the fact that some bodies fall faster to the ground than others, that fact is fully accounted for by the greater resistance which the air offers to the falling of lighter bodies than to the falling of heavier. A particles of bodies, and all bodies, tend to fall with the same velocity, and, in fact, all do; for though, for the reason just stated, a feather will take longer to reach the ground than an ounce of lead, an ounce of lead will fall as fast as a hundredweight. And that it is the resistance of the air, and not any diminution in the power of attraction, which causes the feather to lag behind, may be proved by experiment; for if you let a feather and a coin drop together from the top of the exhausted receiver of an air-pump, they will both be seen to descend at the same rate, and reach the bottom at the same instant; a fact which may be demonstrated more simply by placing the coin and feather free of each other in a paper cone, and letting the cone fall with its apex downwards, so as to break the air's resistance; or by suspending a piece of gold-leaf in a bottle, and letting the bottle drop—of course short of the ground—in which case the included leaf will be seen to have gone as fast and as far as the bottle.

It is to be especially noticed that attraction is no lopsided affair; that it is mutual; that, while the larger body attracts the less, the less also attracts and moves the larger in proportion; and that, indeed, every body and every particle attracts every other, far as well as near, to the utmost verge of the universe of matter. Under it the moon maintains its place with reference to the earth, the planets with reference to the sun, and the solar system with reference to the stellar. As for the moon, it maintains its orbit and revolves round the earth under the action of two forces, the one akin to that by which a ball is projected from the mouth of a cannon, and the other the attraction of the earth, which, by its constant and equal operation, bends its otherwise rectilineal track into a circular one, as we might show if we could only project a ball with such a force as exactly to balance the power of gravity, so that it would at no point in its course be drawn nearer the earth than at starting.

That the force we are considering pervades the solar system is demonstrable, for it is on the supposition of it and the laws it is known to obey that all the calculations of astronomy—and they never miscarry—are grounded; and it is by noticing disturbances in the otherwise regular movements of certain planets that astronomers have been led more than once to infer and discover the presence of some hitherto unknown body in the neighbourhood. It was actually thus the planet Neptune was discovered in 1846. Certain irregularities had been observed in the movements of Uranus, which could not be accounted for by the influence of any other bodies known to be near it; and these irregularities, being carefully watched and studied, gradually led more than one astronomer first to the whereabouts, and then to the vision of the disturbing planet.

Notwithstanding what we said about the universality of this force, and how it affects all forms of matter, it may still appear as if the air were an exception. But it is not so; the air also gravitates. The fact that it gravitates is proved in various ways. First, if it did not, it would not accompany the earth in its movements round the sun; the earth would sweep along into space, and leave it behind it. Secondly, if we place a bottle from which the air is exhausted in a balance and exactly poise it with a counter-weight, and then open it and let in the air, it will show at once that the air has weight or gravitates by immediately descending. Thirdly, if we extend a piece of india-rubber over the end of a vessel and begin to withdraw the air from it, we shall see the india-rubber sink in, under the pressure of the air outside, to fill up the space left vacant by the removal of the included air. The fact that air gravitates we have already taken for granted in explaining the ascent of a balloon; and the proofs now given are enough to show that the cause assumed is a real one. The lighter gas rises and the heavier sinks by law of gravitation.

Gravitation and Cohesion.—Unlike the attraction of aggregation, or cohesion, which acts only between particles separated from each other by spaces that are imperceptible, gravitation takes effect at distances which transcend conception, but it diminishes in force as the distance increases. The law according to which it does so is expressed thus; its intensity decreases with the square of the distance; that is to say, at twice the original distance it is 1-4th; at thrice, 1-9th; at four times, 1-16th, for 4, 9, 16 are the squares respectively of 2, 3, and 4. To take an instance, a ball which weighs 144 lb. at the surface of the earth will weigh 1-4th of that, or 36 lb., when it is twice as far from the centre as it is at the surface; and 1-9th, or 16 lb. when it is thrice as far; and 1-16th, or 9 lb. when it is four times as far. The attraction of cohesion, on the other hand, as we say, acts only when the particles seem almost in contact, and it ceases altogether when once, by mechanical or other means, the bond is broken, in consequence of the particles being forced too near, or sundered too far from, one another.

One distinguishing difference between the attraction of gravitation and that of cohesion is, that whereas the former is uniform, the latter is variable; that is, under gravitation the attraction of any one particle to any other is the same, but under cohesion, some sets of particles are more forcibly drawn together than others. For instance, a particle of iron and a particle of cork gravitate equally, but particles of iron and particles of cork among themselves do not cohere equally. And it is just because those of the former cohere more than those of the latter, that a piece of iron feels harder and weighs heavier than a piece of cork.

Further, the attraction of gravitation is unaffected by change in the condition of bodies, while that of cohesion is. It makes nothing to gravitation whether a piece of metal is as cold as ice, or heated with a sevenfold heat. Not so to the power of cohesion; withdraw heat, and the particles under cohesion cling closer; add it, and both the spaces grow wider and the attraction feebler. Thus, for example, you may suspend a weight by a piece of copper-wire, and the wire not break. But apply heat to the wire, and its cohesion will be lessened; the force of gravitation will overpower it, rupture the wire, and cause the weight to fall.

Cohesion.—That the action of the attraction of cohesion depends on the contiguity of the particles in the cohering body, may be shown by an illustration. Take a ball of lead, divide it into two hemispheres, smooth the surfaces of section, then press them together, and you will find it requires some force to separate them; thus proving the dependence of cohesion on contiguity, although the effect in this case may be due in some degree to the pressure of the atmosphere as well as the power of cohesion.

Heat is the principal agent in inducing cohesion, as well as in relaxing its energy; for by means of it you can weld the hardest as well as the softest substances into one, and two pieces of iron together, no less than two pieces of wax. It is possible, indeed, by heat to unite two sufficient waxed corks to one another, so as to be able by means of the one to draw the other out of a bottle: such, in this case, is the force of cohesion induced by heat.

The power of cohesion exists between the particles of liquids as well as those of solids, the only difference being that in solids the particles are relatively fixed, while in liquids they move freely about one another, unless indeed when they are attracted to the surface of a solid—a fact we are familiar with when we dip our finger into a vessel of water. The cohesive power of liquids is overcome by heat as well as that of solids, only to a much greater degree, for under it they assume a new form, acquire new properties, and expand immensely in volume. They pass into the form of vapour, occupy a thousand times larger area, and possess an elasticity of compressibility and expansibility they were destitute of before.

There is a beautiful phenomenon which accompanies the expansion of ether under the influence of heat. Placed in a flask to which heat is applied, the ether will go off in vapour; and as the heat increases, the vapour will gradually light up into a lovely flame. The expansibility of air, which is vapour in a permanent form, can be shown by experiment. If we tie up an empty or collapsed bladder, and place it in a vessel over an air-pump, we may see, as we withdraw the air from the vessel, and so diminish its pressure, the bladder gradually expand and swell as it does under inflation.

The cohesive power of water is beautifully illustrated. Have a small barrel or bucket so constructed as to be fitted with gauze at the top; immerse it exactly, so that the water may form a film between the meshes, and then open the tap at the bottom: the water will not flow till the meshes at the top are broken by blowing on their surface. The adhesion of the particles in a soap-bubble is another illustration, no less beautiful, as well as more familiar; for the soap, which might be supposed to be the cause of the phenomenon, serves only to prevent the intrusion of dust between the particles, but by no means to intensify their attractive power.

There are some liquids the adhesiveness of whose particles is so perfect as to bar out the access of air when we strew them on the surface of other liquids; and on the Continent it is not uncommon to protect wines against the action of the atmosphere by, instead of corking the bottle, simply pouring in a few drops of oil, which, being lighter than the wine, floats on the surface. It is parallel to the instance of the barrel with the gauze-wire top mentioned above, that if we loosely plug a bottle full of liquid with a piece of cotton-wool, and invert it, the particles in contact with the wool will cohere so closely that the fluid will not be able to escape. The adhesiveness of the particles of water to a solid surface can be exemplified by allowing one of the scales of a balance to float in water and leaving the other free; the one in contact with the water will refuse to yield after we have placed even a tolerable weight in the other which is suspended in the air.

The power of cohesion is more rigorous in some bodies than others. In some cases the body will rupture if it is interfered with ever so little; in others, the particles admit of a certain displacement, and if the limits are not transgressed, they return to their original position when the compressing or distending cause is removed. This rallying power in the cohesive force is called Elasticity, and it exists in no small degree in glass. The spaces between the particles can, within limits, be either lessened by compression or increased by distension, and the particles retain their power of recovering and maintaining the relation they stood in before they were disturbed. It is the power of cohesion or aggregation which resists any disturbance among the particles, and which restores order among them when once disturbance has taken place. And not only does nature resist directly any undue interference with the cohering force, but tampering with it even slightly has often a certain deteriorating effect upon the physical properties of bodies. A bell, for instance, loses its tone when heated, because by that means its particles are disturbed; though it recovers its tone-power as it cools, and as the particles return to their places.

In organic bodies, both during growth and decay, the particles are more or less in flux; but in feathers, after their formation, the attraction of aggregation remains constant, and by means of it their particles continue fixed in their places, not only with the life of the bird, but long after. Nay, you may even crumple them up, and toss them away as worthless, and yet if you expose them to the vapour of steam, they will not only recover their form, but they can be made to look as beautiful as ever.

Chemical Affinity.—The attraction of the particles of bodies of different kinds to each other is often striking and curious; as, for instance, those of salt to those of water. The salt attracts the water, and the water the salt, till at last, if there is a sufficient quantity of water, all the salt is attracted particle by particle from itself, and taken up and united to the water. The salt is no longer visible to the eye, and is said to be dissolved or in solution; but this change of form is due to its affinity for the water, and the resulting attraction of the one to the other. The same phenomena are observed, and they are due to the same cause, in other solutions; as when we infuse our tea or sweeten it with sugar. The attraction of water, or one of its elements rather, for other substances, sometimes shows itself in vehement forms. When a piece of potassium, for example, is thrown into a vessel of water, its attraction for the water is such, and of the water for it, that it instantly takes fire, and the two blaze away, particle violently seizing on particle until the elements of the water unite part for part with the metal. It is the mutually attractive force that causes the heat and flame which accompany the combination; and this force is most violently active in the union of dissimilar substances. Unions of a quieter kind, though not less thorough, occur even between solids when placed in contact. For instance, sulphate of soda and sulphate of ammonia, when placed side by side, will diliquesce, and in liquid form unite into a new combination. Sulphuric acid, when we mix it with water, generates great heat; and this is due to its attraction for the water. Sometimes two fluids unite together, and, in doing so, pass from the liquid into the solid form; as, e.g., sulphuric acid and chloride of calcium. Attraction of this nature is called chemical: it takes effect between dissimilar particles, and results in combinations with new properties. It operates not only between solid and solid, solid and liquid, and liquid and liquid, but between these and gases, and gases with one another; and these as well as those combine into new substances, and evince in the act not a little violent commotion. Thus, phosphorus catches fire in the atmosphere at a temperature of 140 degrees, and it goes on rapidly combining with the oxygen, burning with a dazzling white light, and producing phosphoric acid. Indeed, most metals have an affinity for the oxygen in the air, and oxydise in it with more or less facility; and a metal, as such, has more value than another according as it has less affinity for that element, and is less liable to oxydise or rust in it. This is one reason, among others, why gold is the most precious metal, and the conventional representative of highest worth in things.

There are some metals, such as lead, for instance, which oxydise readily, but this process stops short at the surface in contact with the air, and so forms a coating which prevents the metal from further oxydation; so that here, as in so many things else, strength is connected with weakness.

Electricity.—This, in the most elementary view of it, is a more or less attractive or repellant force latent in bodies, and which is capable of being roused into action by the application of friction. It is excited in a rod of glass by rubbing it with silk, and in a piece of sealing-wax by rubbing it with flannel, though the effect is different when we apply first the one and then the other to the same body. Thus, e.g., if we apply the excited sealing-wax to a paper ring, or a pith-ball, hung by a silk thread from a horizontal glass rod, it will, after contact, repel it; and if, thereafter, we apply to it the excited glass rod, it will attract it; or if we first apply the excited glass rod to the paper ring, or pith-ball, it will, after contact, repel it; and if thereafter we apply to it the excited sealing-wax, it will attract it. The reason is, that when we once charge a body by contact with either kind, it repels that kind, and attracts the opposite; if we charge it from the glass, i.e., with vitreous electricity, it refuses to have more, and is attracted to the sealing-wax; and if we charge it from the sealing-wax, i.e., with resinous electricity, it refuses to have more, and is attracted to the glass-rod; only it is to be observed that, till the body is charged by either, it has an equal attraction for both. From all which it appears that kindred electricities repel, and opposite attract, each other.

Two pieces of gold leaf suspended from a metal rod, inserted at the top of a glass shade full of perfectly pure, dry air, will separate if we rub our foot on the carpet, and touch the top of the rod with one of our fingers; for the motion of the body, as in walking, always excites electricity, and it is this which, as it passes through the finger, causes the phenomenon; though the least sensation of damp in the glass would, by instantly draining off the electricity, defeat the experiment. What happens in this case is, that one kind of electricity passes from the finger to the leaves, while another kind, to make room for it, passes from the leaf to the finger; and the leaves separate because they are both more or less charged with the same kind of electricity, and kindred electricities repel each other. Ribbons, particularly of white silk, when well washed, are similarly susceptible of electrical excitation; and they behave very much as the gold leaf does when they are rubbed sharply through a piece of flannel. Gutta-percha is another substance which, when similarly treated, is similarly affected.

This power is a very mysterious one, and of a nature to perplex even the philosophic observer. Certain bodies, such as the metals, convey it, and are called conductors; certain others, such as glass and porcelain, arrest it, and are called insulators. It is for this reason that the wires of the telegraph are supported by a non-conductor, for if not, the electric current would pass into the earth by the first post and never reach its final destination. Glass being an insulator, it was found that, if a glass bottle was filled with water, and then corked up with a cork, through which a nail was passed so that the top of it touched the water, it would receive and retain a charge as long as it was held in the hand; and this observation led to an invention of some account in the subsequent applications of electricity, known, from the place of its conception, as the Leyden jar. This is a glass jar, the inside of which is coated with tinfoil, and the outside as far as the neck, and into which, so as to touch the inside coating, a brass rod with a knob at the top is inserted through a cork, which closes its mouth. By means of this, in consequence of the isolation of the coatings by the glass, electricity can, in a dry atmosphere, be condensed, and stored up and husbanded till wanted.

A series of eggs, arranged in contact and in line, give occasion to a pretty experiment. In consequence of the shells being non-conductors, and the inside conducting, it happens that a current of electricity, applied to the first of the series, will pass from one to another in a succession of crackling sparks, in this way forcing itself through the obstructing walls. This effect of electricity in making its way through non-conducting obstructions accounts for the explosion which ensues when a current of it comes in contact with a quantity of gunpowder; as it also does for the fatal consequences which result when, on its way from the atmosphere to the earth, it rushes athwart any resisting organic or inorganic body.

Magnetism.—Unlike electricity, which acts with a shock and then expires, magnetism is a constant quantity, and constant in its action; and it has this singular property, that it can impart itself as a permanent force to bodies previously without it. Thus, there being natural magnets and artificial, we can, by passing a piece of steel over a magnet, turn it into a strong magnet itself; although we can also, when it is in the form of a horse-shoe, by a half turn round and then rubbing it on the magnet, take away what it has acquired, and bring it back to its original state. The magnetic property is very readily imparted (by induction, as it is called) to soft iron, but when the iron is removed from the magnetising body, it parts with the virtue as fast as it acquired it. To obtain a substance that will retain the power induced, we must make some other election; and hard steel is most serviceable for conversion into a permanent magnet.

The properties of the magnet are best observed in magnetised steel; and when we proceed to test its magnetic power, it will be found that it is most active at the extremities of the bar, which are hence called its poles, and hardly, if at all, at the centre; that while both poles attract certain substances and repel others, the one always points nearly north and the other nearly south when the bar is horizontally suspended; and that, when we break the bar into two or any number of pieces, however small, each part forms into a complete magnet with its virtue active at the poles, which, when suspended, preserves its original direction; so that of two particles one is, in that case, always north of the other; nay, it is probable that each of these has its north pole and its south, as constant as those of the earth itself, which, too, is a large magnet.

The magnet acts through media and at a distance, as well as in contact; and it has an especial attraction for iron, the more so when the conducting medium is solid, such as a table; and so when the magnet is horizontally suspended, or poised, in the vicinity of iron, its tendency to point north and south is seriously disturbed. The disturbance of the bar, or needle, in such a case, is called its deflection; and it is corrected by so placing a piece of soft iron or another magnet in its neighbourhood as to neutralise the effect, and leave said bar, or needle, free to obey the magnetism of the earth. The needle, it is to be remarked, does not point due north and south, neither, when poised freely on its centre, does it lie perfectly horizontal; in our latitude it points at present 20 deg. west of north, which is called its declination, and its north pole slopes downwards at an angle of 68 deg., which is called its dip.

By holding a rod of iron, or a poker, for a length of time parallel to the direction of the needle, so as to have the same declination and the same dip, it will gradually assume and display magnetic virtue, and this will ere long become fixed and powerful under a succession of vibratory shocks. There is a beautiful experiment in which a needle, when magnetised, can be made to float on water, when it adjusts itself to the magnetic meridian, and will incline north and south the same as the needle of the compass.

The Chemical Action of Electricity and Magnetism.—These agents possess powers which develop wonderfully in connection with chemical combination. Thus, if we suspend a piece of iron in a vessel which contains oxygen gas, and apply to the metal an electric current, it will immediately begin to unite rapidly, and form an oxide with oxygen, emitting, during the process, intense heat and a bright flame. Zinc, too, when similarly acted on, will ignite in the common atmosphere and burn away, though with less intensity, till it also is, under the electric force, reduced to an oxide. It is presumed that many other chemical combinations take place because of the simultaneous joint development of electric agencies, as in copper, water, and aquafortis, nitrate of copper, &c. So also it happens that, when a plate of iron is for some time immersed in a copper solution, it comes out at length covered over with a coating of copper. And it is because there is electricity at work that a silver basin will be coated with copper when we pour into it a copper solution, and at the same time place in it a rod of zinc, so that it rests on the side and bottom, though no coating will form at all when there is no rod present to excite the electric current. The same phenomena will appear if we deposit a silver coin in the solution in question: the coin will come out unaffected, unless we excite affinity by means of a rod of iron. It is under the action of an electric current that one metal is coated with another. The metal, copper say, is steeped in a solution of the coating substance, and connected by means of wires with a galvanic battery, under the action of which the metal in solution unites with the surface of the plate immersed in it. Heat also is developed under magnetic influence, and that often of great intensity. Thus, if we connect the poles of a voltaic battery by means of a platinum wire, heat will develop to such a degree that the platinum will almost instantaneously become red hot and emit a bright light, and that along a wire of some considerable length. A similar effect is noticeable when we substitute other metals, such as silver or iron, for platinum. And the electric light, which flashes out rays of sunlike brilliance, is the result of placing a piece of compact charcoal between the separated but confronting poles of a powerful galvanic battery, light, developing more at the one pole and heat more at the other of the incandescent substance.

Kindred, though much milder, results will show themselves under simpler, though similar, contrivances. A flounder will jump and jerk about uneasily if we lay it upon a piece of tinfoil and place over it a thin plate of zinc, and then connect the two with a bent metal rod; which will happen to an eel also, if we expose it to a gentle current from a battery.

By means of electric or magnetic action we can separate bodies chemically combined, as well as unite them into chemical compounds; as will appear if we place a piece of blotting paper upon tinfoil, and this upon wool; if we then spread above these two pieces of test-paper, litmus and turmeric, the one the test of acids, and the other of alkalis, and saturate both with Glauber salt (which is by itself neither an acid nor an alkali, but a combination of the two), and, finally, connect each by means of a piece of zinc with the poles of a battery, the test-papers will immediately change colour, as they do the one in the presence of an acid simply, and the other of an alkali simply, but never in a compound where these are neutralised; thus proving that the compound has in this case been decomposed, and its elements disintegrated one from another.

A very powerful magnet can be produced by coiling a wire round a bar of soft iron, and attaching its extremities to the poles of a galvanic battery, when it will be found that its strength will be proportioned to the strength of the current and the turns of the coil. This is especially the case when the bar is bent into the form of a horse-shoe, and the wires are insulated and coiled round its limbs. The force communicated to a magnet of this kind, which is often immense, is the product of the chemical action which goes on in the battery, and, in a certain sense, the measure of it. How great that is we may judge when we consider that, evanescent as it is in itself, it has imparted a virtue which is both powerful and constant, and ever at our service.

Summary.—Thus, then, on a review of the whole, we find all things are endowed with attractive power, and that there is no particle which is not directly or indirectly related, in manifold ways, to the other particles of the universe. There is, first, the universal attraction of gravitation, under which every particle is, by a fixed law, drawn to every other within the sphere of existence. There is, secondly, the attraction of cohesion or aggregation, which acts at short distances, and unites the otherwise loose atoms of bodies into coherent masses. There is, thirdly, the power by which elements of different kinds combine into compounds with new and useful qualities, known by the name of chemical affinity. And, lastly, related to the action of affinity, aiding in it and resulting from it, there are those strange negative and positive, attractive and repellant polar forces which appear in the phenomena of electricity and magnetism, agencies of such potency and universal avail in modern civilisation.

On the permanency of such forces and their mutual play the universe rests, and its wonderful history. With the collapse of any of them it would cease to have any more a footing in space, and all its elements would rush into instant confusion. What a Hand, therefore, that must be which holds them up, and what a Wisdom which guides their movements! Verily, He that sends them forth and bids them work His will is greater than any one—greater than all of them together. How insignificant, then, should we seem before Him who rules them on the wide scale by commanding them, while we can only rule them on the small by obeying them! And yet how benignant must we regard Him to be who both wields them Himself for our benefit and subjects them to our intelligence and control!

FOOTNOTES:

[B] This paper on "Attraction" is the substance of a lecture which I composed on the basis of notes taken by me when. I had the honour of attending the Prince of Wales at the course given, on the same subject by the late Professor Faraday. The Professor, having seen the resume I had written, warmly commended the execution, and generously accorded me his sanction to make any use of it, whether for the purpose of a lecture or otherwise, as might seem good to me. It is on the ground of this sanction I feel warranted to print it here.



THE OIL FROM LINSEED.

Various processes have for a long time been in use for the purpose of extracting the oils from different species of nuts and seeds, a few of the more interesting of which are not unworthy of brief notice and description.

In Ceylon, where cocoa-nuts and oil-producing seeds abound, the means employed by the natives in the last century for extracting the oils were of a most primitive character. A few poles were fixed upright in the ground, two horizontal bars attached to them, between which a bag containing the pulp of the seed or nut was placed. A lever was then applied to the horizontal bars, which brought them together, thus creating a pressure which, by squeezing the bag, gradually expressed the oil from the pulpy substance. This rude machine was at that time of day one of the most approved for the purpose.

The system of pestle and mortar was also in use, but as the process was necessarily very slow, this method was seldom resorted to. An improvement on this system was invented by a Mr. Herbert, whose design it had been to construct a powerful and efficient machine which should combine cheapness and simplicity. It consisted of three pieces of wood, viz., an upright piece fixed in the ground, from the lower and upper extremities of which there projected the two other pieces, the top one attached to the joint of a long horizontal lever, and the lower one to the joint of a vertical one. The fixed upright post and the horizontal lever formed the press. The bag of pulp being put between the upright one and the vertical, the pressure was obtained by suspending a negro or a weight from the lever.

In another press of the same or a similar kind, the bags were placed in a horizontal frame, and a loose beam of wood pressed down on it by a lever.

Another form of press had cambs and wedges; also a modification of it by Mr. Hall of Dartford, who applied the pressure by means of a steam-cylinder. The cambs are arranged alternately, so that one is filled while the other is being pressed. This brief notice will suffice to give an idea of such machines as are wrought by lever pressure.

We pass on, therefore, to later inventions and improvements.

First, The Dutch or stamper press, invented in Holland; second, the screw; and, third, the hydraulic:—

(1.) The stamper press is something like a beetling-machine, in which wedges are driven in between the bags, containing, of course in a bruised condition, the seed to be pressed.

(2.) The screw press has an ordinary square-threaded screw, and it acts in the same way as press for making cider or cheese.

(3.) The hydraulic press. Here the pressure is produced by means of a piston driven up by the force of water, the immense power of which is, in great part, due to its almost total incompressibility. This is by far the most perfect form of press. Its power must be familiar to all who remember the lifting of the tubes of the Britannia Bridge, and the launching of the Great Eastern.

An oil-mill is in form something like a flour-mill. The operation begins at the top, where the seed is passed through a flat screw or shaker and then through a pair of rollers, which crush it. These rollers are of unequal diameter, the one being 4 feet, and the other 1 foot; but they are both of the same length, 1 foot 4 inches, and make fifty-six revolutions in a minute. By this arrangement it is found the seed is both better bruised and faster than when, as was formerly the case, the rollers were of the same diameter. A pair of rollers will crush 4-1/2 tons of seed in eleven hours, a quantity enough to keep two sets of hydraulic presses going.

After the seed is crushed in this way, it is passed under a pair of edge stones. These stones weigh about seven tons, are 7 feet 6 inches in diameter and 17 inches broad, and make seventeen revolutions a minute. If of good quality, they will not require to be faced more than once in three years, and they will last from fifteen to twenty. They are fitted with two scrapers, one for raking the seed between the stones, the other for raking it off at the proper period. One pair of stones will grind seed sufficient for two double hydraulic presses, and the operation occupies about twenty-five minutes. The seed is now crushed and ground, but before it is passed on to the press it is transferred to the heating-kettle.

The heating-kettle is composed of two cylindrical castings, one fitting loosely into the other, so that a space is left between them for a free circulation of steam all round both the sides and bottom of the interior vessel. The internal casting is again divided horizontally into two partitions, one above the other therefore, by two plates, between which also there is a space left for the admission and circulation of steam; and a communication is kept up between the upper compartment and the under by means of a stripping valve. Besides this, there is a communication from the internal kettle through the external one, and also a shaft passes between the two horizontal parts to give motion to the stirrer, which revolves thirty-six times a minute. A cover encloses the top, and it is through this the vessel is charged. The upper portion is filled first, where the contents introduced are allowed to remain ten or fifteen minutes, after which the valve is opened and the whole falls into the lower kettle, where it is kept till wanted. The seed is then taken away from the lower kettle by an opening, and bestowed in bags of sufficient size to make a cake of 8 lbs. weight after the oil is pressed out of it. Indeed, the compartments of the heating-kettle are of a size to contain enough to charge one side of a hydraulic press. These, therefore, are so constructed as to render the operation continuous, the upper one being discharged into the under as soon as its contents are withdrawn to the press. The seed is heated to the temperature of 170 degrees Fahr., when it is drawn off and placed in the bags.

In another form of kettle the seed is heated on a hot hearth, and on the top of the hearth is a loose ring, within which a spindle revolves to stir the seed. After the requisite temperature has been reached, the ring is raised and the seed swept into the bags, which are made of horse-hair. There is great loss of heat in this method, however, as the seed is exposed to the atmosphere, which of course cools it.

We now come to the final operation, the mode of expressing the oil. The screw press we do not need to describe, as it consists simply of two plates, brought together by a screw, in the same way as the press used for squeezing apples in the manufacture of cider, and the cheese press. Let us look therefore at the stamper press. It consists of an iron box, open at the top, at each end of which are two plates, capable of containing between them a bag of seed which shall yield a cake weighing 9 lbs. To one of the inner plates of the box is attached a wedge, beside which is inserted another filling up, and then the driving wedge is introduced; and lastly, another block is let in between this wedge and the other plate as soon as the bags have been placed vertically in the press-box. A stamper of wood, worked by cambs on a revolving shaft, is allowed to fall about 1 foot 10 inches, at the rate of fifteen strokes a minute, for about six minutes. This stamper is 16 feet long by 8 inches square, and falls on the head of the wedge, and drives it in to a level at the top of the box. Another stamper is employed to drive down an inverted wedge, so as to release the working one, and enable the attendant to take out the cake. A press of this kind will turn out only about 12 cwts. of cake a day.

We come now to the hydraulic press. This is certainly the most approved invention that has yet been adopted, and it is simply a Bramah press adjusted for the purpose. It has been in use for about thirty years, though it was, of course, at first less skilfully and scientifically constructed than it is now. In one of the earliest of these presses, the box which contains the seed runs on a tramway in order to facilitate its removal from the heating-kettle, so that each time the bags have to be replenished the whole box has to be removed; and this causes no inconsiderable loss both of power and time, for it has, when filled, to be replaced on the ram and lifted bodily upwards in order to bring it flush with the top of the press, which fits the press-box and acts as a point of resistance. In this arrangement there are introduced only one press and one set of small pumps.

The next press we come to is Blundell's, which is admitted to be by far the most efficient in use to-day. Here there are two distinct presses, or a double hydraulic press, fed by two pumps, one 2-1/2 inches and the other 1 inch in diameter, both connected with the separate cylinders by hydraulic tubing. The stroke of these pumps is 5 inches, and they make thirty-six strokes a minute. The larger pump is weighted to 740 lbs. on the square inch, and the smaller to 5540 the square inch. The diameter of the rams is 12 inches, and the stroke 10 inches. Each press is fitted to receive four bags of seed, and it produces 64 lbs. of cake at each operation. After the heated seed has been placed in the bags, the attendant proceeds to fill one press, and then he opens the valve between the large pump and the charged press, which causes the ram to rise till there is a pressure of forty tons, whereupon the safety-valve of the large pump opens, and is kept so by a spring. While this operation is going on, the attendant is occupied with filling the second press; which completed, he opens the communication between the large pump and the second press, taking care first to replace the safety-valve. The ram of this press is then raised to the same height as the other, after which the safety-valve rises a second time. The attendant, as he closes the valve which opens the communication between the large pump and the press, at the same time opens the valve between the small pumps and the presses; and the pressure, amounting to about 300 tons, exerted by the small pump, is allowed to remain on the rams for about seven minutes. From which it appears that, allowing three minutes for emptying and charging the press, the process of expressing the oil takes only three minutes in all; and it is done by this press in this brief time in the most effectual manner. The oil, as it is expressed, passes through the canvas and hair bags to a cistern, known as the spill-tank, which is just large enough to contain the produce of one day's working. The presses are worked by oil instead of water, as it keeps both presses and pumps in better order. Each of them will produce 36 cwts. of cake per day of eleven hours, while the yield of oil is about 14 cwts. The oil is pumped from the spill-tanks to larger ones, capable of holding from 25 to 100 tons, where it remains for some time in order to settle previously to being brought to the market.

I do not intend to enter into the relative merits of the various presses, but content myself with having explained to you the manner in which the oil is produced.

Before concluding, it may be interesting to give you some idea of the vast extent of this manufacture. It appears, according to the official returns, that in the year 1841 we imported 364,000 quarters of seed.

THE OIL FROM LINSEED.

1842 368,000 1847 439,000 1852 800,000 1843 470,000 1848 799,000 1853 1,000,000 1844 616,000 1849 626,000 1854 828,000 1845 666,000 1850 668,000 1855 757,000 1846 506,000 1851 630,000 1856 1,100,000

Now if we take the last year's imports, we shall find that the produce would amount to about 144,000 tons' weight of oil-cake, and above 56,000 tons of oil.

The cake is used for feeding cattle, and the oil for burning, lubricating, painting, &c.; and a very large quantity is exported.

We find that to crush the seed imported in 1856 it required from 150 to 160 double hydraulic presses, nearly 100 of which were in Hull. This shows the extent of our commerce in the seed of flax, to say nothing of its fibre; and is one more instance of the great results which may be wrought out of little things. What a beautiful illustration of the bounty of Providence; and what an encouragement to the ingenuity of man! Who knows what treasures may yet lie hidden in neglected fields, or to what untold wealth the human family may one day fall heir?



HODGE-PODGE: OR, WHAT'S INTILT.

WRITTEN NOV. 20, 1875, AT STAGENHOE PARK.

The subject and treatment, as well as title, of this Lecture are suggested by the answer of the hostess at a Scottish inn to an English tourist, who was inquisitive to know the composition of a dish which she offered him, and which she called Hodge-Podge. "There's water intilt," she said, "there's mutton intilt, there's pease intilt, there's leeks intilt, there's neeps intilt, and sometimes somethings else intilt." The analysis was an exhaustive one, and the intelligence displayed by the landlady was every way worthy of the shrewdness indigenous to her country; but her answer was not so lucid to her listener as to herself, as appeared by his bewildered looks, and his further half-despairing interrogatory. "But what is intilt?" said he, impatiently striking in before she had well finished. "Haven't I been tellin' ye what's intilt?" she replied. And she began the enumeration again, only with longer pause and greater emphasis at every step, as if she were enlightening a slow apprehension,—"There's water intilt, there's mutton intilt;" quietly and self-complacently adding, as she finished, "Ye surely ken now what's intilt." Whether her guest now understood her meaning, or whether he had to succumb, contented with his ignorance, we are not informed; but few of my readers need to be told that "intilt" is a Scotch provincialism for "into it," and that the landlady meant by using it to signify that the particulars enumerated entered as constituents into her mysterious dish.

My aim is to discourse on the same constituents as they display their virtues and play their parts on a larger scale, in a wider economy; and when I have said my say, I hope I may be able to lay claim to the credit of having spoken intelligibly and profitably, though I must at the outset bespeak indulgence by promise of nothing more than the serving up of a dish of simple hodge-podge. The question I put in a wider reference is the question of the Englishman, as expressed in the Scotchwoman's dialect, What's intilt? and I assume that there enter into it, as radically component parts, at least the ingredients of this motley soup. Into the large hodge-podge of nature and terrestrial economics, as into this small section of Scotch cookery, there enter the element of water, the flesh of animals, and the fruits of the earth, as well as the processes by which these are brought to hand and rendered serviceable to life. The ingredients of hodge-podge exist in rerum natura, and the place they occupy and the function they fulfil in it are no less deserving of our inquisitive regard.

Thus, there is water in it, without which there were no seas and no sailing of ships, no rivers and no plying of mills, no vapour and no power of steam, no manufacture and no trade, and not only no motion, but no growth and no life. There is mutton, or beef, in it, and connected therewith the breeding and rearing of cattle, the production of wool, tallow, and leather, and the related manufactures and crafts. There are turnips and carrots in it, the latter of such value to the farmer that on one occasion a single crop of them sufficed to clear off a rent; and the former of such consequence in the fattening of stock and the provision of animal food, that a living economist divides society exhaustively into turnip-producing classes and turnip-consuming. There are leeks and onions in it, and these, with the former, suggest the art of the gardener, and the wonderful processes by which harsh and fibrous products can be turned into pulpy and edible fruits. And there are pease and barley in it, and associated therewith the whole art of the husbandman in the tillage of the soil and the raising of cereals, with the related processes of grinding the meal, baking the bread, preparing the malt, brewing the beer, and distilling the fiery life-blood at the heart.

Now, to discourse on all these, as they deserve, would be a task of no ordinary magnitude, but the subject is an interesting one, and to treat of it ever so cursorily might not unprofitably occupy a reflective moment or two. Water is the first topic it is laid upon me to talk about, and I begin with it all the more readily because it suggests a sense of freshness, and thoughts which may float our enterprise prosperously into port.

I. Water, as already hinted, is an element of vast account in the economy of nature, and is a recreation to the heart and a delight to the eye of both man and beast. To have a plentiful supply of it is one of the greatest blessings of God to the creature, and to be able to bestow it wisely and employ it usefully is one of the most serviceable of human arts. It is too valuable a servant to suffer to go idle, and many are the offices it might do us, if, as it travels from the mountains to the sea-board, we caught it in its course, harnessed it to our chariot, and guided it to our aim. We should turn it to account every inch of its progress, and compel it, as it can, to minister to our requirements by its irresistible energy. Its merely mechanical power is immense, and this is due in great part to its incompressibility; for it is in virtue of this quality alone we can, by means of it, achieve feats not otherwise feasible. How else could we have raised to its sublime height that stupendous bridge which spans the Menai Straits, and which is the wonder of the beholder, as it is the boast of the designer? It stands where it does by the help of some mechanism indeed, but the true giant that lifted it on his shoulders and bore it to its airy elevation was the incompressible force of water, a fluid which is, strangely, the simple product of the combination of two elastic transparent gases, oxygen and hydrogen, neither of which apart has the thew and sinew of its offspring. Nay, it is this single element, which, acted on by heat or acting through machinery, fetches and carries for us over the wide globe, and is fast weaving into one living web the far-scattered interests of the world.

Water was in primitive times utilised into a motive power by the help of a mechanism of rude design, which yet is hardly out of date, and might recently be seen in its original, still more in modified form, in certain back-quarters of civilisation. A stream, guided by a sluice, was made to play upon four vertical paddle-blades, attached to a shaft which they caused to revolve, and which moved a millstone, resting upon another through which it passed. It was a primitive mill, which superseded the still more primitive hand-mill, or quern; and I myself have seen it at work in the Shetland Islands, and even the north of Scotland, though it is now done away with even there, still more farther south, and its place supplied and its work done by overshot and under-shot wheel-gear, and improved machinery attached, of less or more complexity. One of the most recent improvements is the Turbine, a sort of Barker's mill; it is of great power, small compass, and acts under a good fall with a minimum expenditure of water-power.

Passing from the consideration of water as a motive power in its natural state, I ask you to notice briefly the gigantic force it can be made to develop under the action of heat. In its normal form the power of water is due, as I have said, to its incompressibility; in the state of vapour, to which it is reduced by heat, its power is due to the counter force of expansion. It was when confined as a state prisoner in the Tower of London that the Marquis of Worcester began to speculate on the possibilities of steam, though he little dreamed of its more important applications, and the incalculable services it might be made to render to the cause of humanity. Suddenly, one day, his musings in his solitude were interrupted by the rattling of the lid of a kettle, which was boiling away on the fire beside him, when, being of a philosophic vein, he commenced to inquire after the cause; and he soon reasoned himself into the conclusion that the motive power lay in the tension of the vapour, and that the maintenance of this must be due to successive additions of heat. The thought was a seed sown in a fit soil, for it led to experiments which confirmed the supposition, and inaugurated others that have borne fruit, as we see. It was a great moment in the annals of discovery, and from that time to this the genius of improvement has moved onward with unprecedented strides; and this in the application of steam-power as well as the results, stupendous as these last have been. For as there is no department of industry that has not made immense advances since, none on which steam has not directly or indirectly been brought to bear with effect; so there has been no end to the ingenuity and ingenious devices by which steam has been coaxed into subjection to human use and made the pliant minister of the master, man. All these results follow as a natural consequence from the first discovery of its motive power by the Marquis of Worcester, and the subsequent invention of James Watt, by which the force detected was rendered uniform, instead of fitful and spasmodic, as it had been before. And yet, important as was the discovery of the one, and ingenious as is the invention of the other, both are of slight account in the presence of the great fact of nature observed by the English nobleman and humoured by the Scottish artisan. The genie whom the one captured and the other tamed, is the great magic worker, apart from whose subtle strength their ingenuity had been wasted, and had come to naught.