The point in which this process differs from the old and unsuccessful ones formerly tried, is in the expulsion of the carbon disulphide. It was imagined that it was necessary to expel it by means of heat or steam. Now, when wool moist with bisulphide is heated, it invariably turns yellow. No heat must, therefore, be employed. As already remarked, the solvent is expelled with cold water.

The residue, after distillation of the carbon disulphide, is a grayish colored, very viscous oily matter, still retaining a little bisulphide, as may be perceived from the smell. It has not the composition of ordinary suint, inasmuch as it contains no carbonate of potash, and indeed little mineral matter of any kind. A sample which I analyzed lost in drying 36.2 per cent., the loss consisting of water and carbon disulphide. It gave a residue on ignition amounting only to 1.6 per cent. of the original fatty matter, or 2.5 per cent. of the dried fat. The oil appears, from some experiments which I made, to be a mixture of a glycerine salt and a cholesterine salt of fatty acids. It distills without much decomposition, giving a brown-yellow oil, which fluoresces strongly, and has a somewhat pungent smell. The molecular weight was determined by saponification with alcoholic potash, and subsequent titration of the excess of potash employed. This was found to equal 546.3. This would correspond to a mixture of 18.7 parts of stearate, palmitate, and oleate of glycerine, with 81.3 parts of the same acids combined with cholesteryl. But this is largely conjecture. The boiling point of the oil is high, much above the range of a mercurial thermometer, so that it is difficult to gain an insight into its composition.

An objection which has been raised to this process is that the use of such an easily inflammable substance as bisulphide of carbon is attended by great risk of fire. Were the bisulphide to be exposed to free air, there might be force in this objection; but there is no reason why it should ever be removed from under a layer of water. The apparatus, to make all safe, should not be under the same roof as the mill; and no open fire need be used in the building set apart for it. It is easy to rotate the centrifugal machine by a belt from the mill, but better by a small engine attached, the power for which can be conducted by a small steam-pipe, and the distillation of the bisulphide can also be conducted without danger by the use of steam, as its boiling point is a very low one. The question may be naturally asked, "How do the wool and fabric made from the wool scoured by this process, compare with that scoured in the usual way?" To answer this question I may refer to a test made by Messrs. Isaac Holden & Co., at their works at Roubaix. A sample of wool was divided into two portions, one of which was scoured by the usual method, and the other by the turbine or Mullings' process. Skilled workers then span each sample to as fine a thread as possible. Now the thinness to which a wool can be spun is evidence of its power of cohesion—in other words, its strength. The weight of 1,000 meters of the wool cleaned by the new process bore to that scoured by the old process the proportion of 1,015 to 1,085, showing that a considerably finer thread had been produced. And in total quantity, 67.53 kilos. of the former corresponded to 71.77 kilos. of the latter, showing a proportionately less waste. Such fine yarn had never before been obtained from similar wool. The yarn of the soap-washed wool could not be spun, for it could not withstand the strain; whereas, that scoured by the new process gave an admirable thread.

Another test to which it was subjected may be cited. It is the custom in France, before the wool is scoured, to put it through a sorting process, by which all the short lengths are weeded out. On a quantity exceeding 11,000 kilogrammes, half of which was scoured by the turbine process, and half by the ordinary process, the former in scouring lost in weight 2 per cent. less than the latter, although the short length extracted from the moiety thus treated weighed only 10 kilogrammes, while that taken from the other weighed over 150 kilogrammes. This saving, even with the unequal treatment, amounted in value to from 30 to 40 centimes per kilogramme.

In order that the importance of this application may be realized, I shall conclude with some figures:

The raw wool imported into England, in the year 1882, amounted to 1,487,169 bales, its total value being about 22,000,000. The cost of washing this wool by the old process, with carbonate of soda, amounts to about d. per lb. of the raw material. The cost for the total quantity of wool imported is at least 1,214,000. But it is customary to wash wool with soap, especially for the combing trade, and the cost is then about 1d. per lb. The cost of scouring by the new process is about 1 5s. per ton, or 0.13d. per lb. Taking the least favorable comparison, were all the imported wool (home-grown wool is here left out of the calculation, for want of sufficient returns) cleansed by the turbine process, the actual saving would be 1,214,500 minus 315,700, or nearly 900,000 per annum.

It is thus seen that there is room for a very important economy in the treatment of wool. I have endeavored to show how economy may be practiced in scouring by the old process with soap, and how one dye stuff may be profitably recovered. It is to be hoped that means of extracting other dyes from the residue may soon follow. Unless the process were too costly to repay the trouble of extraction, it would be well worth practicing; for it would not merely be a solution of the problem of how to avoid waste, but would at the same time prevent the pollution of our streams, now, unfortunately, only too rarely pellucid; and were the last process to have as successful a future as I hope it may have, a very important saving of expense would result, and a large quantity of valuable fatty matter would no longer be thrown away.

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COAL AND ITS USES.

[Footnote: From a paper lately read before the Association of Foremen Engineers.]

By JAMES PYKE.

The records from which geologists draw their information can scarcely be compared to written or printed histories. There are, however, nations of whom no written account exists, who perhaps never had any written history, but about whom we are still able to gather from other sources a vast amount of information. Their houses, their monuments, their weapons, and their tools have survived, and these tell us the kind of life, the state of civilization, and the skill of the men to whom they belonged; from the contents of their tombs we learn what manner of men they were physically; sometimes a sudden change in the appointments and belongings of the folk indicates that tribes which had for a long time inhabited a district were driven out and replaced by a new race. Thus, then, from waifs and strays we can piece together a fairly connected account of the events of a period long antecedent to any written history.

The investigations of Dr. Schliemann on the supposed site of the city of Troy furnish a good example of this method of research. He found lying, one on the top of another, traces of the existence of five successive communities of men, differing in customs and social development, and was able to establish the fact that some of the cities had been destroyed by fire, and that later on other towns had grown up over the buried remains of the earlier settlements. The lowest layers were, of course, the oldest, and the position of each layer in the pile gives its date, not in years, but with regard to the layers above and below it.

Now, from time immemorial nature has been at work building up monuments and providing tombs which tell us what were the events going on, and what kind of inhabitants the earth had long before man made his appearance on its surface. The monuments are the rocks which compose the ground under our feet, and these, like many ancient monuments of human construction, are the tombs of the creatures that lived while they were being built.

Many facts testify that the earth's crust did not come into existence exactly as we find it now, but that its rocks have been built up by the slow action of natural agencies. These rocks constantly inclose the remains of plants and animals, and as it is evident that neither plant nor animal could have lived in the heart of a solid rock, this fact shows that the rock must in some way have gathered round the remains that are now found in it. Again, many of these remains, or fossils, belonged to animals that lived in water, the larger part, indeed, to marine creatures. This indicates that the rock was formed beneath the sea, and when we examine the way in which the constituents of the rock are arranged, we frequently find it to correspond exactly with the manner in which the sand and mud that rivers sweep down into the sea or lakes are spread out over the bottom of the water. In a pile of rocks formed in this way it is clear that the lowest is the oldest of all, and that any one stratum lying above is younger than the one beneath it. Further, the occurrence of rocks inland containing marine fossils far above the sea level shows that the sea and land have changed places. When, again, we find that the fossils of one group of rocks differ entirely from those of a group lying above them, we learn that one race of creatures died out and was supplanted by a new assemblage of animal forms.

These general remarks will, I trust, give some notion of the evidence which is available for reconstructing the history of those remote periods with which geology deals, and of the kind of reasoning which the geologist employs for interpreting the records that are submitted to him.

We will now briefly examine, by aid of these methods, the group of rocks in which coal occurs in Great Britain, and see how far we can read the story they have to tell.

The group with which we have to deal is called the carboniferous or coal bearing system, and it includes four classes of rocks, viz.: 1, sandstone; 2, shale or bind; 3, limestone; 4, coal and underclay.

We will take the sandstones and shales first. They are grains of sand known to mineralogists as quartz, and consisting of a substance called silica by chemists. The grains of sand are bound together by a cement which in some few cases is identical in composition with themselves, and consists of pure silica, but usually is a mixture of sandy, clayey, and other substances. The shales are made up very largely of clay, mixed, however, usually with sand and other substances, forming a conglomerate. Both sandstones and shales are divided into layers or beds, and are said to be stratified. It is this stratified or bedded structure that gives us the first clew to the way in which these rocks were formed. Rivers are constantly carrying down sand and mud into the sea or lakes, and when their flow is slackened on entering the still water the materials they bring down with them sink and are spread out in layers over the bottom. The structure of the sandstones and shales shows that they were formed in this way; they often inclose the remains of plants that have been carried down from land, and occasionally of animals that lived in the water where they were deposited.

The next we have to consider is limestone, which is mainly made up of a substance known to chemists as calcium carbonate, or carbonate of lime.

In some districts, especially in volcanic countries, springs occur very highly charged with carbonate of lime. The warm springs of Matlock are a case in point; they are probably the last vestige of volcanic action which was in operation in that neighborhood during carboniferous times. Limestone is chiefly formed by the agency of small marine creatures of low organization. By the aid of these animals the carbonate of lime is brought back to a solid form; at their death their hard parts fall to the bottom and accumulate in a mass of pure limestone, which afterward becomes solidified into limestone rock.

The information that limestone gives us is this:

When we find, as is often the case, a mass of limestone hundreds of feet thick, and composed of little else but carbonate of lime, we know that the spot where it occurs was, at the time it was formed, far out at sea, covered by the clear water of mid ocean; and when we find that this limestone grows in certain directions earthy and impure, and that layers of shale and sandstone, thin at first, but gradually thickening out in a wedge-shape form, come in between its beds, we know that in those directions we are traveling toward the shore lines of that sea whence the water was receiving from time to time supplies of muddy and sandy sediment.

The next class of rocks are the clays that are found beneath every bed of coal, and which are known as underclays, or warrant, or spavins. They vary very much in mineral composition. Sometimes they are soft clay; sometimes clay mixed with a certain portion of sand; and sometimes they contain such a large proportion of silicious matters that they become hard, flinty rock, which many of you know under the name of gannister. But all underclays agree in two points: they are all unstratified. They differ totally from the shales and sandstones in this respect, and instead of splitting up readily into thin flakes, they break up into irregular lumpy masses. And they all contain a very peculiar vegetable fossil called Stigmaria.

This strange fossil was for a long time a sore puzzle to fossil botanists, and after much discussion the question was fairly solved by Mr. Binney by the discovery of a tree embedded in the coal measures, and standing erect just as it grew, with its roots spread out into the stratum on which it stood. These roots were Stigmaria, and the stuff into which they penetrated was an underclay. Sir Charles Lyell mentions an individual sigillaria 72 feet in length found at Newcastle, and a specimen taken from the Jarrow coal mine was more than 40 feet in length and 13 feet in diameter near the base. It is not often these trees are found erect, because the action of water, combined with natural decay, has generally thrown them down. They are, however, found in very large numbers in the roof of the coal, evidently having been tossed over, and lying there flat and squeezed thin by the pressure of the measures that lie above them.

Lastly, we come to coal itself—a rock which constitutes a small portion of the whole bulk of the carboniferous deposits, but which may be fairly looked upon as the most important member of that group, both on account of its intrinsic value and also from the interest that attaches to its history. That coal is little else but mineralized vegetable matter is a point on which there has for a long time been but small doubt. The more minute investigations of recent years have not only placed this completely beyond question, but have also enabled us to say what the plants were which contributed to the formation of coal, and in some cases even to decide what portions of those plants enter into its composition. It is a thing so universally admitted on all hands, that I shall take it for granted you are all perfectly convinced that coal has been nothing in the world but a great mass of vegetable matter. The only question is: How were these great masses of vegetable matter brought together? And you must realize that they were very large masses indeed. Just to take one instance. The Yorkshire and Derbyshire coal field is somewhere about 700 to 800 square miles in area, and Lancashire about 200. Well, in both these coal fields you have a great number of beds of coal that spread over the whole of them with tolerable regularity and thickness, and very often with scarcely any break whatever. And this is only a very small portion of what must have been the original sheet of coal, so that you see we have to account for a mass of vegetable matter perfectly free from any admixture of sand, mud, or dirt, and laid down with tolerably uniform thickness over many hundreds of square miles.

At one time it was supposed that coal was formed out of dead trees and plants which were swept down by rivers into the sea, just in the same way as shales and sandstones were formed out of mud and sand so swept down. The fatal objection to this theory, however, is that rivers would not bring down dead wood alone, but they would bring down sand and mud, and other matters, and that in the bottom of the sea the dead wood would be mixed with these matters, and instead of getting a perfectly unmixed mass of vegetable matter, we should get a mixture of dead plants, sand, mud, and other things, which would give rise to something like coal, but something very different, as any one who tries to burn such coal will soon find out, from really good, pure house coal. So that this theory, which is generally known as the "drift" theory, was totally inadequate to account for the facts as we know them.

The other theory was that coal was formed out of plants and trees that grew on the spot where we now find coal itself. On this supposition it is easy to account for the absence of foreign admixtures of sand, mud, and clay in the coal; and we can also understand very much better than by the aid of the drift theory how the coal had accumulated with such wonderful uniformity of thickness over such very large areas. This theory was for some time but poorly received; but after the discovery of Sir William Logan, that every bed of coal had a bed of underclay beneath, and the discovery of Mr. Binney, that these underclays were true soils on which plants had undoubtedly grown, there was no doubt whatever that this was the real and true explanation of the matter.

I dare say many of you have had occasion to walk across peat bogs. The peat bog is a great mass of vegetable matter, which is every year growing thicker and thicker; and underneath it there is almost always a bed of thin clay, in look very much like the underclays, and this thin clay is penetrated by the rootlets of the moss forming the peat, exactly the same way as the underclays of the coal measures are penetrated by the stigmaria and its rootlets. But you must not suppose that the plants out of which coal was formed were exactly the same low type of moss which forms our present peat bogs. However, it is pretty certain that they were for the most part of a loose, succulent texture, and that they grew very rapidly indeed.

You will have noticed that there is one step more wanted to make good this theory of the growth of coal on the spot where we now find it. The coal is found, as already described, interbedded with shales and sandstones. These shales and sandstones, as shown, were formed beneath the water of the sea, and as long as they remained there of course no plants could grow upon them. The question is, How was the land surface formed for the growth of plants? It must have been formed in some way or other by the sea bottom having been raised above the level of the water. Now, we have distinct proof in many cases that elevation of the sea bottom and depression of the land is now going on in many parts of the earth's surface. And, therefore, we shall be assuming nothing beyond the range of experience if we say that such elevations and depressions went on during coal measure times. The coal measure times must have been times during which the same spot was now below the sea, and now dry land, over and over again. There was a land surface on which plants grew fast and multiplied rapidly, and as they died fell and accumulated in a great heap of dead vegetable matter. After a time this layer of vegetable matter was slowly and gently let down beneath the waters of the sea—so slowly that the water flowing over it did not, as a rule, disturb the loose, pasty mass; and then, by the method I have described to you, shales and sandstones were deposited on the top of this mass of dead vegetable matter. By their weight they compressed it, and by certain chemical changes (which we have not time to go into this evening) this dense mass of vegetable matter became converted into coal. After a time the shales and sandstones which had been piled above this stuff, which was to form coal for the future, were again elevated to form a land surface; upon this another forest sprang up, and by its decay produced another mass of vegetable matter fit to form coal. This again was let down below the water, more shales and sandstones were deposited on the top, and this process went on over and over again till the whole mass of our present coal measures was formed. You will now see how it is that trees are so seldom found in an upright position in the coal beds. As the land went down, they would in very many cases be toppled over by the water as it flowed against them, or their base would be rotted, and they would then either fall or be blown over; that is the reason why in most cases they are found lying flat on the roof of the coal bed. But in a few cases, when the depression was very gentle and gradual, the trees were not overthrown, and the shales and sandstones accumulated round them and preserved them in the position in which they grew.

I do not know that I can point out to you anything nowadays that exactly resembles the state of things that must have gone on during the times these coal measures were being formed; but there are a great many cases strikingly analogous to them. I shall not attempt to describe them to you, but may just mention the mangrove swamps that very often fringe the coasts in the tropics, and the cypress swamps of the Mississippi, which are so well described by Sir Charles Lyell in his recent works; also the great Dismal Swamp of Virginia, which appears to me to furnish the nearest analogue to the state of things that existed during coal measure times.

Having explained the way in which coal measures have been formed, we will now take a brief sketch of its uses and products. The year 1259 is memorable in the annals of coal mining. Hitherto the mineral had not been raised by authority, but in that year Henry III. granted a charter to the freemen of Newcastle-on-Tyne for liberty to dig coal, and a considerable export trade was established with London, and it speedily became an article among the various manufacturers of the metropolis. But its popularity was but short lived. An impression became general that the smoke arising therefrom contaminated the atmosphere and was injurious to public health. Years of experience have proved the fallacy of the imputation; but in 1306 the outcry became so general that a proclamation was issued by Edward I forbidding the use of the offending fuel, and authorizing the destruction of all furnaces, etc., of those persons who should persist in using it. Prejudice gradually gave way as the value of the fossil fuel became better known, and from that time downward its use has become more and more extended down to the enormous extent of our present trade. The annual increase in the production of coal in the British Isles since the year 1854 is over 2 million tons. In that year the coal produce was about 65 million tons, and it has grown up to the year 1880 to the grand total of 135 million tons.

We will now deal with some of the uses that this valuable black diamond is now being put to. It is, in the first place, the center of all our enterprise and prosperity, and upon it depends our chief success as a manufacturing nation for the future. When it is exhausted we shall have to look forward to the condition of things which now obtains in those regions where there is no coal—that is to say, instead of our being a nation full of manufacturing and mercantile enterprise, a great nation to which all the people of the earth resort, we shall be merely a people who live for ourselves by the cultivation of the ground. The duration of our coal fields has been ascertained within certain limits. Mr. Hall, an accomplished geologist, tells us that in England at the present time we have a stock of coal sufficient for our consumption for no less than 1,000 years. On the other hand, Professor Jevons, whose opinion is worthy of the very greatest weight on such questions, calculates that 100 years is about the tenure of our coal fields, according to the present rate of increase in the consumption. Whichever view we take, sooner or later the end must ultimately come when the coal will be exhausted; when the great mainspring of our commercial enterprise will be gone, and we shall revert to that condition in which we were before the coal fields were worked. In this point of view, therefore, coal has an especial interest to us as engineers. If coal is important in this direction, it is no less important in a purely scientific point of view, apart from any mercantile end.

The chemist or physicist will tell you the wondrous story that the black substance which you burn is simply so much light and heat and motion borrowed from the sun and invested in the tissues of plants. He will tell you that when you sit round your firesides the flame which enlivens you, and the gas which enables you to read, and which civilizes you, is nothing in the world but so much sunlight and so much sunheat bottled up in the tissues of vegetables, and simply reproduced in your grates and gas burners. Very few persons, I am afraid, realize this, which is one of the many stories which science in its higher teachings shows us—one of those fairy tales which are the result of the most careful scientific investigation. Of the hundred and odd million tons of coal which we in this country burn in the course of a year, about 20,000,000 tons are thrown on our house fires; 30,000,000 tons find their way into our blast furnaces, or are otherwise used in the smelting and manufacture of metals; about 48,000,000 are burnt under steam boilers; 6,000,000 are used in gas-making; while the remainder is consumed in potteries, glass works, brick and lime kilns, chemical works, and other sundries which I need not speak of.

To go into the chemistry of coal is quite sufficient to take up more time than I have at my disposal this evening, therefore I will briefly touch on a few of the main points. Coal gas is made, as you are all aware, by heating coal or cannel, which is the special form of coal most valued for the purpose, on account of the high quality of gas it produces in cylindrical fireclay retorts.

The by-products obtained in the manufacture of coal gas, the tar and the ammonia water, are nowadays scarcely less important than the coal gas itself. The ammonia water furnishes large quantities of salts to be used, among other applications, as food for plants. We thus restore to-day to our vegetation the nitrogen which existed in plants of primeval times. The tar, black and noisome though it be, is a marvelous product, by the reason of scores of beautiful substances which are concealed within it.

Coal tar when distilled yields three main products: naphtha, dead oil, and pitch or asphalt. The naphtha on redistillation yields benzine, from which are prepared some of our most beautiful dyes; the dead oil, as the less volatile portion is termed, furnishes carbolic acid, used as a disinfectant and antiseptic, together with anthracene and naphthaline; all three substances the starting points of new series of coloring matters.

This discovery of these coloring matters marks an era in the history of chemical science; it exercised an extraordinary influence on the development of organic chemistry. Theoretical and applied chemistry were knit together in closer union than ever, and dye followed dye in quick succession; after mauve came magenta, and in close attendance followed a brilliant train of reds, yellows, oranges, greens, blues, and violets; in fact, all the simple and beautiful colors of the rainbow.

But there is still another story of coal tar to be told. Among the many curious substances that wonderful fluid contains is the beautiful wax-like body called paraffine, the development of which chiefly owes its origin to the genius and energy of Mr. James Young. As early as 1848, Mr. Young had worked a small petroleum spring in a coal mine in Derbyshire, and had produced oils suitable for burning and lubricating purposes, but the spring gave out, and then Mr. Young sought to obtain these oils by distilling coal. After many trials, in conjunction with other gentlemen connected therewith, he proved successful, and the present magnitude of this industry is without parallel in the history of British manufactures.

In Scotland alone there are about sixty paraffine oil works, one alone occupying a site of nearly forty acres. Here about 120,000 gallons of crude oil are produced weekly, and among the various works in Scotland about 800,000 tons of shale are distilled per annum, producing nearly 30,000,000 gallons of crude oil, from which about 12,000,000 gallons of refined burning oil are obtained in addition to the large quantities of naphtha, solid paraffine, ammonia, and other chemical products. Twenty-five years ago scarcely a dozen persons had seen this paraffine, and now it is turned out by the ton, fashioned into candles delicately tinted with colors obtained from coal tar.

I might dwell on this subject until it becomes wearisome to you, therefore I will not trespass too much on your time. But from every point we look we reach this fact, that our coal trade is one which develops itself according to laws that we are perfectly powerless to control; if it seems to promise a less rapid increase here, it is only that it may spread abroad with accelerated vigor elsewhere; if it is our slave in some aspects, it seems as if it were our master in others.

Finally, we have to ask, What of our export coals? Rapid as has been the growth of our total production during the last twenty-three years, the growth of our export of coals has been greater still. Beginning at 4,300,000 tons in '54, we find it reaching 16,250,000 tons in '76, and an increase at a corresponding ratio up to the present date as far as statistics will carry us. At such a rate of increase it would seem as if our whole annual production would be ultimately swallowed up in our exports, and it is not, perhaps, impossible that after we have ceased to be to any great extent a manufacturing people, a certain export trade in coal may still continue. Just the same as the export trade in coal preceded by centuries our own uses for it other than domestic, so may it also survive these by a period as prolonged. If our descent from our present favored position be a gradual one, much may be done in the interval to adapt ourselves to the future outcome, but it is certain that nothing will be done except under the stern persuasion of necessity.

When our coal fields become exhausted, be it soon or late, he would be a wise or, perhaps, a rash speculator who fixed himself to a year or a generation. Being inevitable, the best philosophy is to make our decline more gradual and less bitter. Sentimental regrets that these hills and valleys will no longer resound with the din of labor, or be blackened by the smoke of the factory, would surely be out of place. What we might regret is that Britain, which we know and are proud of, the Britain of great achievements in politics and literature, of free thought and self-respecting obedience, of a thousand years of high endeavor and constant progress, was indeed to perish when these factories and furnaces whirled and blazed their last. But, it is not so. This country's fortunes are gradually being merged into those of a Greater Britain, which largely, through the aid of coal, whose prospective loss we are lamenting, has grown beyond the limits of these islands to overspread the vastest and richest regions of the earth; and we have no reason to fear that the great inheritance that America and Australia and New Zealand have accepted from us will in their hands be dealt unworthily with in the future.

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GASTON PLANTE.

This eminent scientist was born in Orthez (Department of Basses-Pyrnes) on the 22d of April, 1834; at present in his fiftieth year. He began his scientific career as assistant to Edmund Becquerel at the Conservatoire des Arts et Mtiers at Paris. In the year 1859, after resigning his position at the above named institution, he entered upon his researches in electricity, and has continued them ever since. His work entitled "Recherches sur l'Electricit" is a model of clear language and elegant demonstration, and contains all the papers presented by Plant to the Paris Academy of Sciences since 1859.



At the Paris Electrical Exhibition in 1881, Plant received a Diploma of Honor, the highest distinction conferred, while in the same year the Academy of Sciences voted him the "Lacaze" prize, and the Society for the Encouragement of National Industry presented him with the "Ampre" medal, its highest award.

Plant deserves not only the honors conferred upon him by his own country, but those of the world on account of his cosmopolitan character—a rarity among his countrymen. He sends his apparatus to all exhibitions of any consequence; they appeared at Munich and Vienna, where their interpretation by the attendant added considerably to the renown of their author.—Zeitch f. Elektrotechnik.

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WARREN COLBURN.

Warren Colburn, the eminent American mathematician, was born in Dedham, Mass., March 1, 1793.

He was the eldest son of a large family of children. His parents were poor, and "Warren" was, during his childhood, frequently employed in different manufacturing establishments to aid the family by his small earnings.

In early boyhood he manifested an unusual taste for mathematics, and in the common district school was regarded as remarkable in this department. He learned the trade of a machinist, studying winters, until he was over twenty-two years of age, when he began to fit for Harvard College, which he entered in 1817 and graduated with high honors in 1820. He taught school in the winter months, while in college, in Boston, Leominster, and in Canton, Mass. From 1820 to 1823 he taught a select school in Boston.

While in college he was regarded as by far the best mathematician in his class, and during this period thought there was the necessity for such a book as his "First Lessons in Intellectual Arithmetic." This conviction had been forced upon his mind by his experience in teaching. In the autumn of 1821 he published his "first edition." His plan was well digested, although he was accustomed to say that "the pupils who were under his tuition made his arithmetic for him;" that the questions they asked and the necessary answers and explanations which he gave in reply were embodied in the book, which has had a sale unprecedented for any book on elementary arithmetic in the world, having reached over 2,000,000 copies in this country, and the sale still continues, both in this country and in Great Britain. It has been translated into most of the European languages and by missionaries into many Asiatic languages.

After teaching in Boston about two and one-half years, he was chosen superintendent of the Boston Manufacturing Company's works at Waltham, Mass., and accepted the position; and in August, 1824, owing to the mechanical genius he displayed in applying power to machinery, combined with his great administrative ability, he was appointed superintendent of the Lowell Merrimac Manufacturing Co., at Lowell, Mass. Here he projected a system of lectures of an instructive character, presenting commerce and useful subjects in such a way as to gain attention and enlighten the people.

For several years he delivered gratuitous lectures on the Natural History of Animals, Light, Electricity, the Seasons, Hydraulics, Eclipses, etc. His knowledge of machinery enabled him admirably to illustrate these lectures by models of his own construction; and his successful experiments and simple teaching added much to the practical knowledge of his operatives.

He proposed to occupy the space between the common schools and the college halls by carrying, so far as might be practicable, the design of the Rumford Lectures of Harvard into the community of the actual workers of common life.

In the mean time he discharged his official duties efficiently, and the superintendence of the schools of Lowell was also added to his labors. He never relinquished, during these busy years, the design formed in his college days of furnishing to the children of the country a series of text-books on the inductive plan in mathematics.

His "Algebra upon the Inductive Method of Instruction," appeared in 1825, and his "Sequel to Intellectual Arithmetic" in 1836. He regarded the "Sequel" as a book of more merit and importance than the "First Lessons."

He also published a series of selections from Miss Edgeworth's stories, in a suitable form for reading exercises for the younger classes of the Lowell schools, in the use of which the teachers were carefully instructed.

In May, 1827, he was elected a Fellow of the American Academy of Sciences. For several years he was a member of the Examining Committee for Mathematics at Harvard College.

He was a member of the Superintending School Committee of Lowell; and so busy were he and his coworkers that they were repeatedly obliged to hold their meetings at six o'clock in the morning.

Warren Colburn was ardently admired—almost revered—by the teachers who were trained to use his "Inductive Methods of Instruction" in teaching elementary mathematics.

In personal appearance Mr. Colburn was decidedly pleasing. His height was five feet ten, and his figure was well proportioned. His face was one not to be forgotten; it indicated sweetness of disposition, benevolence, intelligence, and refinement. His mental operations were not rapid, and it was only by great patience and long continued thought that he achieved his objects. He was not fluent in conversation; his hesitancy of speech, however, was not so great when with friends as with strangers. The tendency of his mind was toward the practical in knowledge; his study was to simplify science, and to make it accessible to common minds.

Mr. Colburn will live in educational history as the author of "Warren Colburn's First Lessons," one of the very best books ever written, and which, for a quarter of a century, was in almost universal use as a text-book in the best common schools, not only in the primary and intermediate grades, but also in the grammar school classes.

In accordance with the method of this famous book, the pupils were taught in a natural way, a knowledge of the fundamental principles of arithmetic. By its use they developed the ability to solve mentally and with great facility all of the simple questions likely to occur in the every day business of common life.

Undoubtedly Pestalozzi first conceived the idea of the true "inductive method" of teaching numbers; but it was Mr. Colburn who adapted it to the needs of the children of the common elementary schools. It has wrought a great change in teaching, and placed Warren Colburn on the roll as one of the educational benefactors of his age.

He died at Lowell, Mass., Sept. 13, 1883, at the age of 90 years.—Journal of Education.

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THURY'S DYNAMO-ELECTRIC MACHINE.

Thury's dynamo-electric machine, which presents some peculiarities, has never to our knowledge been employed outside of Sweden and a few neighboring regions; but this is doubtless due to some personal motive or other of its constructors, since it has, it would seem, given excellent results in every application that has been made of it. It is represented in perspective in Fig. 1, and in longitudinal section and elevation in Figs. 2 and 3.

As may be seen, it is a multipolar (6-pole) machine in which an attempt has been made to utilize magnetically, as far as possible, all the iron used in the frame. For this reason the system has been given the form of a hexagonal prism, whose faces are formed of flat electro-magnets, A, A, xxx, constituting the inductors.

The internal angles of this prism are filled by polar expansions, P, P, xxx, alternately north and south, that thus form in the interior of the apparatus an inscribed cylinder designed to receive the armature. This latter belongs to the kinds that are wound upon a cylinder in which the wire is external thereto.

The conductors are placed upon the iron drum longitudinally and parallel with its axis. But instead of being connected with each other at the posterier end of the armature, as in the Siemens system, they are connected according to chords that correspond to a fourth, a sixth, or any equal fraction whatever of the circumference. Fig. 4 gives a perspective view of the cylinder, upon which the conductors 1, 2, 3, 4, and so on, are placed according to generatrices. The armature is supposed to be divided into six parts, each conductor passing over the bases of the drum through a chord equal to the radius, that is to say, corresponding to a sixth of the circumference.

Three conductors are all connected together in such a way as to form but a single circuit closed upon itself. Conductor 1, for example, is connected with No. 6 in such a way that the end issuing from 1 becomes the end that enters No. 6. Conductor No. 3 is connected in the same way with No. 8, and so on, up to the last conductor, which is connected in its turn with the end that enters the first.

As the figure shows, the conductor before passing from 3 to 8, for example, returns several times upon itself in following 6 and 3, and the same is the case with all the rest of the winding.



In this way the cylinder becomes inclosed within nine rectangular wire frames, each of which is connected with the following one by a conductor that is at the same time connected with one of the nine plates of the collector. The number of the rubbers corresponds to that of the inducting poles. They may be coupled in different ways, but they are in most cases united for quantity.

It will be seen that the Thury armature resembles, in the system of winding, those of the Siemens machines and their derivatives. But it differs from these, however, in the details connected with the coupling of the wires, from the very fact that the features of a two-pole machine are not found exactly in a multipolar one.



This latter kind of machine is considered advantageous by its inventors, in that there is no need of revolving it with much velocity. It must not be forgotten, however, that although we reduce the velocity by this mode of construction, we are, on another hand, obliged to increase the size of the machine, so that, according to the circumstances under which we chanced to be placed, the advantage may now be on the one side and now on the other.



It goes without saying that Fig. 4 is essentially diagrammatic, and is designed to give a clearer idea of the mode of winding the armature. In practice the number of the frames, and consequently that of the plates of the conductor, is much greater, and the arrangement that we have described is repeated a certain number of times, the conducter always forming a circuit that is closed upon itself.

The Thury machines are constructed in different styles. No. 1 is a 100-lamp (16 candles and 100 volts) machine, and Nos. 2 and 3 are nominally 250-lamp ones, but may be more. Their weight is 1,100 kilogrammes, and their velocity, for 100 volts, is from 400 to 500 revolutions, according to the mode of coupling.

A later type, now in course of construction, is to furnish from 750 to 2,000 lamps, with 250 revolutions, for 100 volts, and is not to weigh more than 2,000 kilogrammes. Let us add that Messrs. Meuron and Cuenod, the manufacturers, have likewise applied their mode of winding to conductors arranged radially upon the surface of a circle. Fig. 5 shows this arrangement.

In this case the inductors will, it is unnecessary to say, be arranged laterally as in all flat ring machines. The arrangement will recall, for example, that of the Victoria machines (Brush-Mordey).

We do not think that the inventors have applied this radial arrangement practically, for it does not appear to be advantageous. The parts of conductors which are perpendicular to the radius, and which can be only inert (even if they do not become the seat of disadvantageous currents), have, in fact, too great an importance with respect to the radial parts.—A. Guerout, in La Lumiere Electrique.

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BREGUET'S TELEPHONE.

Prof. G. Forbes gives the following description: The instrument which I call Bregut's telephone is founded upon the instrument which was described by Lipmann, called the capillary electrometer. The phenomenon may be shown in a variety of ways. One of the easiest methods to show it is by taking a long glass tube and bending it into two glasses of dilute acid, and, the tube being filled with acid itself, a piece of mercury is placed in the center of the tube. Then if one pole of a battery is connected with one vessel of acid, and the other pole of the battery is connected with the other vessel of acid, at the moment of connection the bit of mercury will be seen to travel to the right or left, according to the direction of the current. M. Lipmann explained the action by showing that the electro-motive force which is generated tends to alter the convexity of the surface of the mercury. The surface of the mercury, looked at from one side, has a convex form, which is altered by the electro-motive force set up when connection is made with the battery. The equilibrium of the mercury is dependent upon the convexity, and consequently when the convexity is disturbed the mercury moves to one side or the other. Lipmann also showed that if a tube containing a bit of mercury, and tapering to a point, is taken and dipped into acid, and then the tube filled with acid, on one pole of a battery being dipped into the tube and another into the acid the mercury will move up or down, showing similar action to that which I have just described.

Lipmann further showed the reverse effect, that if a piece of mercury be forcibly pressed, so as to alter the convexity of its surface, such as by bringing it into a narrower part of the tube, then there is an electro-motive force produced.

It occurred to me, and no doubt it did to Breguet also, that if we speak either against the surface of the glass tube, and caused the tube to vibrate, or if the mercury were caused to vibrate in the manner I have shown, we ought to be able to introduce a varying current in the wires which might have sufficient electro-motive force to produce audible speech in a Bell telephone. Further, the same instrument, since varying electro-motive force affected the drop of mercury and produced varying displacement, ought also to act as a receiving instrument, and should vibrate in accordance with the currents that arrive. My experiments have only been in the way of using the instrument as a transmitter; but Bregut, I find, used it as a receiver as well as a transmitter, though I am not aware that M. Breguet made any actual experiments so as to produce articulate speech. I presume that this was done, although I have not come across any description of the experiments, and it was for that reason that I thought possibly some account of my own experiments might be interesting to the members of the Society. The first tubes that I used were bits of glass tube about a centimeter diameter, and simply drawn out to a tapering point. I have the tubes here. The first experiment I tried was by tapping the glass tube so as to mechanically shift the position of the mercury, and by listening on the telephone for the effect. For a long time, at least an hour, I could get no effect at all. At last I got a sound, but could not understand how it was that at one time of tapping I could not hear, while at another time it was quite loud.

At the top I always got sound, but at the side I got no sound, although the mercury was shaking. I then tried to see how feeble a current was audible in the telephone. An assistant tapped the tube while I stood out of the way, and where I could not see. I got him to tap it gentler and gentler, and could hear the most feeble tap. A pellet of paper was next dropped from various heights down to an inch, and each tap was perfectly audible in the telephone. I tried many methods, and one, purely accidentally chosen, was a piece of glass tube which I had drawn out into a tube about 2 mm. diameter, and then nearly closed the end of it. I have that tube here, and you will see what an ill-shapen and ugly-looking tube it is, but it is one of the best tubes I ever got; and finally, I found that small bits of thermometer tube, which were simply closed at their ends with a blow-pipe, gave very good results, and I was able to make them useful for various purposes. I then tried mounting a tube on the end of a speaking-trumpet and speaking to the mercury, but got no effect. In every place where I attached the glass tube itself to a sounding-board I got a very accurate reproduction. I put one on a piece of ferrotype plate, and that gave really the best result I ever got. The tube was fastened with sealing-wax, and with it I got excellent speech heard in a Bell receiver. I tried putting in a large number of these tubes, all in quantity, on the bottom of a ferrotype plate, but with no advantage. I have not yet tried putting them in series, one behind the other, so as to increase the electro-motive force, but I think that probably would be an improvement; of course it would require many vessels of acidulated water to dip into. The most distinct articulate speech was obtained from an ordinary ferrotype telephone plate, secured at the edges, and one of the glass tubes you see here attached to it.

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MUNRO'S TELEPHONIC EXPERIMENTS.

Mr. J. Munro, whose name is well known not only as a very clear writer upon electrical subjects, but as an original investigator, has recently, with the assistance of Mr. Benjamin Warwick, been conducting a most interesting experimental investigation of the action of the microphone as a telephonic transmitter, with the result of proving that metals may advantageously be employed in the place of carbon in a transmitting instrument, a practical development of one of the very earliest of Professor Hughes' microphones. The fact that metallic electrodes can practically be employed in microphonic transmitters has been denied of late with so much assurance and in such high quarters, that Mr. Munro's successful applications of that portion of Professor Hughes' discovery possess an especial interest, and must to a considerable extent affect the aspect of litigation in future contests in which the discovery of the microphone and the invention of the carbon transmitter are vital points at issue.

In investigating the properties of metallic conductors employed in the construction of microphones, Mr. Munro's first experiments were made with wires. These, in some cases, were caused by the action of a diaphragm, to rub the one on the other in such a manner as to make the point of contact vary (under the influence of the vibrations of the diaphragms) on one side or other of a position of normal potential, so that by the movement of a wire attached to a vibrating tympan along a fixed wire conveying a current from a battery, and thereby shunting the current at various positions along the length of the fixed wire, the strength of the current in the derived circuit, in which was included a suitable receiver, was varied accordingly. In other experiments mercury was employed, either as a sliding-drop, inclosing the fixed wire, or as an oscillating column; but these experiments, though instructive and interesting, did not for various reasons give encouraging results with a view to the practical application of the principle.

They, however, led Mr. Munro to proceed with compound wire structures, such as gratings resting upon or rubbing against one another, and one of the first experiments in this direction proved very successful, and led Mr. Munro to the construction of his gauze telephone, which is the most characteristic and efficient of his practical apparatus.

This instrument consists essentially of two pieces of iron-wire gauze, the one fixed in a vertical plane, and the other resting more or less lightly against it, the pressure between them being regulated by an adjustable spring or weight. These gauze plates are so connected in a telephonic circuit as to constitute the electrodes of a microphone; for touching one another lightly in several points, they allow the current to be transmitted between them in inverse proportion to the resistance offered to it in its passage from one to the other. Under the influence of sonorous vibrations the one plate dances more or less on the other, thus varying the resistance; and very perfect articulation is produced in a telephonic receiver included in the circuit. The gauze transmitter so constructed may be fixed within a wall-box with or without a mouthpiece; but as the sound waves acting directly upon the gauze plates set them into agitation through their sympathetic vibration or by direct impact, no sort of diaphragm or equivalent device is necessary, and none is employed.



A convenient form of this apparatus is shown in Fig. 1, and to which the name of "The Lyre Telephone" has been given from its resemblance to that impossible musical instrument. In this apparatus, G is a plate of iron wire gauze stretched vertically between two horizontal wires attached to a lyre-shaped framework of mahogany; against the plate rests the smaller plate, G, the normal pressure between them being regulated by an adjustable spring acting in opposition to a weighted lever, W. The two plates are connected respectively with the attachment screws, X and Y, by which the instrument is placed in a circuit with a battery and telephonic circuit.



A modification of this apparatus is shown in the diagram sketch, Fig. 2, which will probably be a more practical form. In this instrument the electrodes consist of two circular disks of iron wire gauze of different diameters, the larger disk, G, which is fixed, being pierced with holes of smaller diameter than the smaller disk, G. In the diagram the two disks are shown separated for the purpose of explanation, but in reality they rest the one against the other; the smaller and movable disk, G, is held up against G with greater or less pressure by the spiral spring, S, the tension of which can be adjusted by a screw or other suitable device at N. This form of the apparatus is more suitable for inclosure in a wall box with or without a mouthpiece, but it does not require the employment of any kind of diaphragm or tympan. Mr. Munro can employ with all his instruments an induction coil for installations where the resistance of the line wire makes it desirable to do so; the microphone and battery being included in the primary circuit and the telephones in the secondary.



Fig. 3 is an ingenious arrangement devised by Mr. Munro, in which the adjusting spring or weight is substituted by a magnet which may be either a permanent or an electro-magnet. The figure shows an arrangement in which the fixed gauze, g, is perforated as in the apparatus illustrated in Fig. 2, and the movable electrode, g, is bent or dished so as to press upon g around its edge. E is a magnet which by its attractive influence upon g holds t up against g with a pressure dependent upon its magnetic intensity and upon its distance from the gauze. By making E an electro-magnet, and including its coil in the telephonic circuit, an instrument may be constructed in which the normal pressure between the electrodes can be automatically adjusted to the strength of the current, and in cases where an induction coil is employed the magnet, E, may be the core of such a coil.



Fig. 4 illustrates an apparatus devised by Mr. Munro, and to which the name thermo-microphone might be given, as it is a microphone in which thermo-electric currents are employed in the place of voltaic currents, its special feature of interest lying in the fact that the heated junction of the thermo-electric couple is identical with the microphone contacts of the two electrodes. In this very elegant experiment a piece of iron wire gauze, G, is supported in a horizontal position by a light metallic support, B. To another support. A, is loosely hinged a frame, which at its further extremity carries a little coil of German silver wire, C, which by its weight rests upon the center of the gauze plate, G; and in contact therewith, and to increase the pressure of contact, a little bar weight is laid within the convolutions of the core. The two electrodes, the gauze, and the coil are connected, as shown, to a receiving telephone, T. Upon the application of heat, as from the flame of a spirit lamp placed below, a thermo-electric current is set up throughout the circuit; in this condition the apparatus becomes a very perfect microphone, and when the pressure between the electrodes is properly adjusted it is a very efficient telephonic transmitter, transmitting articulate speech and musical sounds with remarkable clearness and fidelity.



Mr. Munro is, with the aid of Mr. Warwick's manipulative skill, extending this portion of his investigation further by experimenting with gauzes and coils of various metals forming other couples in the thermo-electric series, as well as with iron and other gauzes electrotyped with bismuth and other metals, and we hope in due time to lay the results of those experiments before our readers.

Mr. Munro has, moreover, observed that if two pieces of gauze of identical material and in microphonic contact be heated, a peculiar sighing sound is heard in a telephone connected with them and with a battery, and he attributes this phenomenon to the electrical discharge between the gauze plates being facilitated and increased by the action of heat, but we are rather inclined to trace the effect to the mechanical action of the one gauze moving over the other under the influence of expansion and contraction of the metals by the variable temperature of the flame and convection currents of heated air, such movement producing the sounds just as would be produced if one of the electrodes of an ordinary microphone were as delicately moved by the hand or other agent.



Figs. 5 and 6 illustrate another and distinct form of metallic microphone transmitter designed by Mr. Munro and Mr. Warwick, in which a small chain, preferably of iron, forms the microphonic portion of the apparatus. In Fig. 5, A is a plate of sonorous wood forming a diaphragm or collector of the sonorous waves; to the back of this is attached a short length of chain, C, the opposite ends of which are by the wires, X and Y, included in the telephonic circuit. The points of junction of the links with one another constitute the variable microphonic contacts, and the normal pressure between them is adjusted by the spiral spring, S, the tension of which may be varied by the cord and winding pin, B. Fig. 6 is the section of a transmitter constructed upon this principle, and in which two chains, c and c', are employed attached at one end by a wire, f, to a diaphragm mouthpiece, N, and at their opposite extremities to the adjusting springs, s and s'; an induction coil, D, may be employed if the resistance of the line render it advantageous.



Fig. 7 is a form of pencil microphone experimented with by Mr. Munro, which differs from some of the Hughes' transmitters adopted by Crossley, Gower, Ader, and many others only in the material of which it is composed, Mr. Munro's being of cast iron, while the others to which we have referred are of carbon rods such as are used in electric lighting. In Fig. 7 a light cast-iron bar, i, of the form shown, is supported in holes drilled in two blocks of cast iron, i i', and the pressure between the bar and the blocks can be adjusted by a regulating spring, s. In connection with this apparatus Mr. Munro has observed that rust has no appreciable effect upon the efficiency of the instrument unless it be to such an extent as to cause the two to adhere, or to be "rusted up" together.



We now come to another class of metallic transmitters with which Mr. Munro and his associate have been making experiments, and to which he has given the name "Grain transmitter," since it consists of a box having metallic sides, e e', to which terminal screws, t t', are attached and filled in between with iron or brass filings, granules of spongy iron, or indeed small metallic particles in any form; one of the most efficient transmitters being a box such as is shown in Fig. 8, filled with a quantity of in. screws.



The results of Mr. Munro's experiments have led him to the opinion that the action of the microphone must be attributed to the action of sonorous vibrations upon the air or gaseous medium separating the so-called contact-points of the electrodes, and that across these spaces, or films of gaseous matter, silent electrical discharges take place, the strengths of which, being determined by the thickness of the gaseous strata through which they pass, vary with the motion of the electrodes; and as, according to this hypothesis, the distances of the electrodes from one another is determined by the sound-waves, the sound in that way controls the current.—Engineering.

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APPARATUS FOR MANEUVRING BICHROMATE OF POTASSA PILES FROM A DISTANCE.

Bichromate of potassa piles, especially those single liquid ones that are applied to domestic lighting, all present the grave defect of consuming almost as much zinc in open as in closed circuit, and of becoming rapidly exhausted if care be not taken to remove the zinc from the liquid when the battery is not in use. This operation, which is a purely mechanical one, has hitherto required the pile to be located near the place where it was to be used, or to have at one's disposal a system of mechanical transmission that was complicated and not very ornamental.

In order to do away with this inconvenience, which is inherent to all bichromate piles, Mr. G. Mareschal has invented and had constructed an ingenious system that we shall now describe.



Mr. Mareschal's plan consists in suspending the frame that carries all the battery zincs (Fig. 1) from the extremity of a horizontal beam, and balancing them by means of weights at the other extremity.

The system, being balanced, the lifting or immersion of the zincs then only requires a slight mechanical power, such as may be obtained from an ordinary kitchen jack through a combination that will be readily understood upon reference to Fig. 2. The axis, M, of the jack, on revolving, carries along a crank, MD, to which is fixed a connecting-rod, A, whose other extremity is attached to the horizontal beam that supports the zincs and counterpoises. If the axle, M, be given a continuous revolution, it will communicate to the rod, A, an upward and downward motion that will be transmitted to the beam and produce an alternate immersion and emersion of the zincs.

Upon stopping the jack at certain properly selected positions of the rod, MD, the zincs may, at will, be kept immersed in the liquids, or vice versa. This is brought about by Mr. Mareschal in the following way: The jack carries along in its motion a horizontal fly-wheel, V, against whose rim there bears an iron shoe, F, placed opposite an electro-magnet, E. In the ordinary position, this shoe, which is fixed to a spring, bears against the felly of the wheel and stops the jack through friction. When a current is sent into the electro-magnet, E, the brake shoe, F, is attracted, leaves the fly wheel, and sets free the jack, which continues to revolve until the current ceases to pass into the electro.



The problem, then, is reduced to sending a current into the electro and in shutting it off at the proper moment. This result is obtained very simply by means of an auxiliary Leclauche pile. (The piles got up for house bells will answer.) The current from this pile is cut off from the electro, F, by means of a button, B, when it is desired to light or extinguish the lamps. In a position of rest, for example, the crank, MD, is vertical, as shown in the diagram to the right in Fig. 2. The circuit is open between M and N through the effect of the small rod, C, which separates the spring, R, from the spring, R'. As soon as the circuit has been closed, be it only for an instant, the crank leaves its vertical position, the rod, C, quits the bend, S, and the spring, R, by virtue of its elasticity, touches the spring, R', and continues its contact until the crank, MD, having made a half revolution, the rod, C', repulses the spring, R, and breaks the circuit anew. The brake then acts, and the crank stops after making a revolution of 180, and immersing the zincs to a maximum depth. In order to extinguish the lamp, it is only necessary to press the button, B, again. The axle, M, will then make another half revolution, and, when it stops, the zinks will be entirely out of the liquid. The depth of immersion is regulated by fixing the crank-pin. D, in the apertures, T1, or T2, of the connecting rod. This permits the travel, and consequently the degree of immersion, to be varied.

The device requires three wires, two for connecting the lamp with the battery, and one for maneuvering the apparatus through a closing of the contact, B.

With Mr. Mareschal's system, bichromate of potassa piles may be utilized in a large number of cases where a light of but short duration is required until the battery is exhausted, without the tedious maneuvering of a winch and without inconvenience. The jack permits of a large number of lightings and extinctions being effected before it becomes necessary to wind up its clockwork movement. This operation, however, is very simple, and may be performed every time the battery is visited in order to see what state it is in.

We regard Mr. Mareschal's apparatus as an indispensable addition to every case of domestic electric lighting in which bichromate of potassa piles are used, and, in general, to all cases where the pile becomes uselessly exhausted in open circuit. It will likewise find an application in laboratories, where the bichromate pile is in much demand because of its powerful qualities, and where it is often necessary to order it from quite a distant point.—La Nature.

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MAGNETIC ROTATIONS.

By E. L. VOICE.

The remarkable researches and experiments of Professor Hughes clearly show that magnetism is totally independent of iron, and that its molecules, particles, or polarities are capable of rotation in that metal. It would also appear that by reason of the friction between magnetism and iron, the molecules of the latter are only partially moved, such movement being the result of the tendency of iron to retard magnetic change.

I have found that the magnetic molecules also possess inertia, that they are capable of acquiring momentum, and that their rotation continues for a considerable time after the exciting cause of their rotation has ceased.

These facts may be proved in a very evident manner, inasmuch as induced electric currents are generated by this after rotation, which may be made to light incandescent lamps.

In this case the magnetic rotations are produced in an electro magnet by means of alternate currents supplied by alternating Gramme machine.

In order to better explain the action, it will be necessary to refer to a new electro-motor, which was the subject of an article in the Electrical Review of February 19 last. It is of that type of motor in which the field magnet and armature poles are alternately arranged, and which requires a periodical reversibility of magnetism in the armature to cause the latter to revolve, as in the Griscom motor. The insulating strips in the commutator are sufficiently wide to demagnetize the whole of the machine before reversibility in the armature takes place, and this demagnetization sets up a direct induced current, which is caught in a shunt circuit by the aid of a second commutator, which only comes into action when the first commutator goes out.

When this motor is supplied by a continuous current, it is easy to understand that the induced current which passes through the shunt circuit, and which is caused by the demagnetization, is proportional to the mass of iron and wire of which the machine is composed, or proportional to its inductive capacity. This current is purely a secondary effect, of short duration, and only occurs once at each break of the commutator.

The motor is of such a size that when supplied with a continuous current of proper strength the induced electrical effect in the shunt circuit will light one incandescent lamp. If, however, it is supplied with an alternating current of the same power, it will light eight lamps, and the mechanical power given off is even more than with a continuous current, provided that the alternations from the dynamo do not exceed 6,000 a minute.

At first I was considerably puzzled by this great difference, because in both cases it is impossible for the lamp circuit to be acted upon by the main current. It occurred to me, however, that the rapid alternations of the exciting current from the dynamo, and the consequent speed of magnetic molecular rotation, gave the latter a certain momentum, and that by widening the insulating strips of the first or main current commutator, and proportionately increasing the width of conducting surface in the shunt commutator up to certain limits, this effect would be increased. I found such to be the case, from which I inferred that the increase of induced current in the shunt circuit was on account of its longer duration, by reason of the acquired momentum of the magnetic molecular rotations after the alternating exciting current had ceased.



Those who have facilities for carrying out experiments may prove it in the following manner:

E, in the inclosed drawing, is an electro-magnet whose brushes press on two metallic bands, B and B, fixed to but insulated from the spindle, A. The band, B, is in electrical circuit with the shunt commutator, S, and the main commutator, M; while the band, B, is in contact with shunt commutator, S, and main commutator, M. This contact is made by conducting rods, as indicated. The commutators, as regards their brushes, are so arranged that when M and M are in action, S and S are out of action, and vice versa. The spindle and commutators are rotated by the pulley, P. L is an incandescent lamp in the shunt circuit.

Let us now suppose the apparatus at rest, and the brushes in electrical contact with the main commutators, M and M. The current from an alternating dynamo passes into the magnet, E, and rapidly reverses its polarity. By actuating the pulley, P, the commutators are rotated, when M and M go out of, and the shunt commutators, S and S, come into action, enabling the after current set up in the magnet to light the lamp, L, in the shunt circuit.

In order to make comparative tests, the same apparatus may be supplied with continuous instead of alternating currents. The after current in the former case, however, is much smaller, consisting of one electrical impulse only at each break of the commutator, whereas in the alternating system these impulses are practically continued; the result being that, all things being equal, a far greater number of lamps may be used in the shunt than when supplied by continuous current only, and it would appear that this difference can only be attributed to the fact that the rotatory motion of magnetic molecules, or polarity of the magnet, E, acquires momentum when acted upon by a suitable physical cause, such as alternating currents of electricity; this momentum lasting a sensible time after the cessation of the acting cause.

If we had the gift of magnetic sight, and could see what is going on in the electro-magnet when it is excited by alternating currents, we should probably see the molecules or polarities tumbling over each other at an enormous rate. I do not think, however, that we should see anything but a vibratory motion as regards the iron molecules.—Elec. Review.

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[AMER. MICROSCOP. JOUR.]



LIGHTON'S IMMERSION ILLUMINATOR

The following extremely simple plan for an immersion illuminator was first brought to the notice of microscopists a few years ago, and, in the absence of the inventor, was kindly described by Prof. Albert McCalla, at the meeting of the American Society of Microscopists, at Columbus, O. It consists of a small disk of silvered plate glass, c, about one-eighth of an inch thick, which is cemented by glycerine or some homogeneous immersion medium to the under surface of the glass-slide, s. Let r represent the silvered surface of the glass disk, b, the immersion objective, f, the thin glass cover. It will be easily seen that the ray of light, h, from the mirror or condenser above the stage will enter the slide and thence be refracted to the silvered surface of the illuminator, r, whence it is reflected at a corresponding angle to the object in the focus of the objective. A shield to prevent unnecessary light from entering the objective can be made of any material at hand, by taking a strip one inch long and three-fourths of an inch wide and turning up one end. A hole not more than three-sixteenths of an inch in diameter should be made at the angle. The shield should be placed on the upper surface of the slide, so that the hole will cover the point where the light from the mirror enters the glass. With this illuminator Mller's balsam test-plate is resolved with ease, with suitable objectives. Diatoms mounted dry are shown in a manner far surpassing that by the usual arrangement of mirror, particularly with large angle dry objectives.

Ottumwa, Ia.

WM. LIGHTON.



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FOUCAULT'S PENDULUM EXPERIMENTS.

By RICHARD A. PROCTOR.

Science owes to M. Foucault the suggestion that the motions of a pendulum so suspended as to be free to swing in any vertical plane might be made to give ocular demonstration of the earth's rotation. The principle of proof may be easily exhibited, though, like nearly all of the evidences of the earth's rotation, the complete theory of the matter can only be mastered by the aid of mathematical researches of considerable complexity. Suppose A B (Fig. 1) to be a straight rod in a horizontal position bearing the free pendulum C D suspended in some such manner as is indicated at C; and suppose the pendulum to be set swinging in the direction of the length of the rod A B, so that the bob D remains throughout the oscillations vertically under the rod A B. Now, if A B be shifted in the manner indicated by the arrows, its horizontality being preserved, it will be found that the pendulum does not partake in this motion. Thus, if the direction of A B was north and south at first, so that the pendulum was set swinging in a north and south direction, it will be found that, the pendulum will still swing in that direction, even though the rod be made to take up an east and west position.



Nor will it matter if we suppose B (say) fixed and the rod shifted by moving the end A horizontally round B. Further, as this is true whatever the length of the rod, it is clear that the same fixity of the plane of swing will be observed if the rod be shifted horizontally as though forming part of a radial line from a point E in its length. In these cases the plane of the pendulum's swing will indeed be shifted bodily, but the direction of swing will still continue to be from north to south.

Now, let P O P' represent the polar axis of the earth; a b a horizontal rod at the pole bearing a pendulum, as in Fig. 1. It is clear that if the earth is rotating about P O P' in the direction shown by the arrow, the rod a b is being shifted round, precisely as in the case first considered. The swinging pendulum below it will not partake in its motion; and thus, through whatever arc the earth rotates from west to east, through the same arc will the plane of swing of the pendulum appear to travel from east to west under a b.

But we cannot set up a pendulum to swing at the pole of the earth. Let us inquire, then, whether the experiment ought to have similar results if carried out elsewhere.

Suppose A B to be our pendulum-bearing rod, placed (for convenience of description merely) in a north and south position. Then it is clear that A B produced meets the polar axis produced (in E, suppose), and when, owing to the earth's rotation, the rod has been carried to the position A' B', it still passes through the point E. Hence it has shifted through the angle A E A', a motion which corresponds to the case of the motion of A B (in Fig. 1) about the point E,[1] and the plane of the pendulum's swing will therefore show a displacement equal to the angle A E A'. It will be at once seen that for a given arc of rotation the displacement is smaller in this case than in the former, since the angle A E A' is obviously less than the angle A K A'.[2] In our latitude a free pendulum should seem to shift through one degree in about five minutes.

[Footnote 1: In reality A E moves to the position A' E over the surface of a cone having E P' as axis, and E as vertex; but for any small part of its motion, the effect is the same as though it traveled in a plane through E, touching this cone; and the sum of the effects should clearly be proportioned to the sum of the angular displacements.]

[Footnote 2: In fact, the former angle is less than the latter, in the same proportion that A K is less than A E, or in the proportion of the sine of the angle A E P, which is obviously the same as the sine of the latitude.]

It is obvious that a great deal depends on the mode of suspension. What is needed is that the pendulum should be as little affected as possible by its connection with the rotating earth. It will surprise many, perhaps, to learn that in Foucault's original mode of suspension the upper end of the wire bearing the pendulum bob was fastened to a metal plate by means of a screw. It might be supposed that the torsion of the wire would appreciably affect the result. In reality, however, the torsion was very small.



Still, other modes of suspension are obviously suggested by the requirements of the problem. Hansen made use of the mode of suspension exhibited in Fig. 3. Mr. Worms, in a series of experiments carried out at King's College, London, adopted a somewhat similar arrangement, but in place of the hemispherical segment he employed a conoid, as shown in Fig. 4, and a socket was provided in which the conoid could work freely. From some experiments I made myself a score of years ago, I am inclined to prefer a plane surface for the conoid to work upon. Care must be taken that the first swing of the pendulum may take place truly in one plane. The mode of liberation is also a matter of importance.



Many interesting experiments have been made upon the motions of a free pendulum, regarded as a proof of the earth's rotation, and when carefully conducted, the experiments have never failed to afford the most satisfactory results. Space, however, will only permit me to dwell on a single series of experiments. I select those made by Mr. Worms in the Hall of King's College, London, in the year 1859:

"The bob was a truly turned ball of brass weighing 40 lb.; the suspending medium was a thick steel wire; the length of the pendulum was 17 feet 9 inches. The amplitude of the first oscillation was 6 42', and during the time of the experiment—about half an hour—the arcs were not much diminished. As I had to demonstrate to a large number of spectators, I encountered considerable difficulty," says Mr. Worms, "in rendering the small deviations of the plane of oscillation visible to all. I accomplished it in three different ways." These he proceeds to describe. He had first a set of small cones set up, which were successively knocked down as the change in the plane of the pendulum slowly brought the pointer under the bob to bear on cone after cone. Secondly, a small cannon was so placed that the first touch of the pendulum pointer against a platinum wire across the touch-hole completed a galvanic circuit, and so fired the cannon. Lastly, a candle was placed so as to throw the shadow of the pendulum bob upon a ground-glass screen, and so to exhibit the gradual change of the plane of swing.

The results accorded most satisfactorily with the deductions from the theory of the earth's rotation.



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A NEW LUNARIAN.

By Prof. C. W. MACCORD, Sc.D.

The construction of apparatus for illustrating the motions of the heavenly bodies has often occupied the attention of both mathematicians and mechanicians, who have produced many very ingenious, and in some cases very complicated, combinations. These may be divided into two classes; the object of the first being to represent exactly what occurs—to reproduce the precise movements of the various bodies represented in their true proportions and relations to each other, in respect to distances, magnitudes, times, and phases. When the absolute complexity of the movements of the bodies composing the solar system is considered, it is not so much a matter of wonder that a planetarium which shall thus imitate them is a very delicate and complicated machine as that it should lie within the limits of human ingenuity.

In the second class, the object is to show the nature and the causes of specific phenomena, without regard to others perhaps, and without necessarily paying attention to exact proportions of distances and dimensions. Indeed, it is often the case that the illustration is made clearer by exaggerating some of these and reducing others; thus, for example, the causes of the variation in the lengths of the days and nights, and of the changes in the seasons, can be exhibited to much better advantage by an apparatus in which the diameter of the sun and its distance from the earth are enormously reduced than they possibly could be were they of their proper proportionate magnitudes; nor is the presence of any other planet, or the attendance of a satellite, at all necessary or even desirable for the purpose named.

It is apparent that machines of this class can be made much more simple than those of the first, while at the same time it may safely be asserted that for educational purposes they are far more useful.

In both classes, the action involves the use of some sort of epicyclic train, since the motions to be explained are both orbital and axial. The planetary body is carried round by a train-arm, and its rotation about its axis is usually given it by a train of gearing, the inner or central wheel of which is stationary, being fastened to the fixed frame supporting the whole.



The lunarian which we herewith present belongs to the second of the classes above named; in its construction an attempt has been made to show by as simple means and in as clear a manner as possible the nature of the following phenomena, viz.:

1. Apogee and perigee.

2. The moon's phases.

3. The rotation on her axis, by reason of which she always presents nearly the same face to the earth.

4. The inclination of her axis to the plane of her orbit, and her consequent libration in latitude.

5. Her varying angular velocity, and consequent libration in longitude.

The mechanism consists of a train-arm, T, which turns upon the vertical pivot, P, fixed in the stand. In this arm, T, are the bearings of two cranks, B and C. equal in length to each other and to a third crank, A, which is stationary, being fixed to the pivot, P, by a pin, p. To the crank-pin of A is secured a reverted arm, A', which supports the earth, E, and keeps it also stationary. The three cranks are connected by the rod, R, like the parallel rod of a locomotive: to which is fastened by a steady-pin, o, the bevel wheel, D, concentric with the crank-pin, b. The head of this crank-pin is first made spherical, then faced off at an angle with the axis of b, and in the sloping face is firmly fixed the long screw, S, forming the support for the moon, M, which is caused to rotate about the axis of S, by means of the wheel, F, equal to and engaging with D. The upper end of S projects slightly through a perforation in the moon, and to it the hemispherical black shell or cap, G, is fixed by the screw, K; this cap represents the unilluminated part of the moon, and since G, s, b, and B, are in effect but one piece, the cap moves precisely as the crank does.

Now as the train-arm, T, is carried round, the cranks, B and C, will turn in their bearings; but by their connection with A, they are compelled to remain always parallel to themselves, and thus the axis of the moon receives a motion of translation. But since during this action the wheel D turns relatively to the pin b, the moon evidently rotates about its axis with an angular velocity precisely equal to that of its orbital motion.

The black shell however has the motion of translation only, and thus exhibits the phases of the moon, on the supposition that the source of light is infinitely remote and the rays come always in the same direction, which is not strictly true, of course; but the reasons of the varying appearance are as clearly shown as if it were absolutely exact. The same may be said in regard to the phenomena of libration; the inclination of the moon's axis to the plane of her orbit is really small, but is purposely exaggerated in this apparatus in order to make the results apparent; in the position represented, it is quite obvious that an observer upon the earth can see a little past one pole, and cannot quite see the other, as well as that this condition will be reversed after half a revolution.

The action in reference to the phases is clearly shown in the small diagram on the right. The one on the left illustrates the manner in which the libration in longitude is made apparent. It will be noted that the center of M is not directly over the axis of the bearing of the crank, B, so that after half a revolution the moon will be farther from the earth than she is here shown. Her orbit here is circular, whereas, in fact, it is an ellipse; but the earth not being in the center, her angular velocity in relation to the earth is variable, the result of which is that, when she is near her quadrature, the actual force presented to the earth is slightly different from that presented when in conjunction or opposition.