2. The same results were obtained from rails laid all around the northeast curve, and even after they had acquired a due west to east course; showing that each rail acquired the same magnetic polarity which would be exhibited by any magnetic needle oscillating freely in our northern hemisphere, dipping also at its north end considerably downward if suspended at its center of gravity.

3. Applying the needle at the west terminus, a few anomalies were observed; but, especially nearer the junction, the rails all gave the normal result found on the main track.

4. The wheels of the cars standing on the north and south track followed the same law, exhibiting both vertical and lateral induction, so that the lower rims and the forward or north part of the periphery attracted the unmarked end of the needle, while the upper and rear, or south portions of the periphery of the wheel attracted the marked end.

5. The wheels of cars standing on the east and west road exhibited the following modification. The lowest rim of all the wheels, whether standing on the north rails or on the south rails of said track, in consequence of vertical induction attracted the unmarked end of the needle, and the upper rims attracted the marked end of the needle; but the middle portions of the periphery, both anterior and posterior, of the wheels standing on the north rail, attracted the unmarked end, while similar middle portions of wheels standing on south rails attracted the marked end; in consequence of horizontal induction, the wheels being connected by iron axles, and thus presenting considerable extension across the track, viz., from south to north.

Magnetite seems to have acquired its polarity in the same manner, namely by the earth's induction, when the ore contains a large enough percentage of pure iron. A large specimen (6 in. long by 31/2 deep and weighing 51/2 lb.) which I obtained from near Pilot Knob, Missouri, exhibits polarity, not only at its lateral ends, but also vertically, as the lower surface attracts the unmarked end of a needle, while the plane, which evidently occupied the upper surface in its native bed, attracts the marked end of the needle.

Iron fences invariably exhibit only the polarity by vertical induction; so also small buckets, bells, etc. But in the case of a bell about 3 ft. in diameter at its base, and over two feet deep, tapering to about a foot in diameter at the top, I found that although the top attracted the marked end of the needle, the bottom attracted the unmarked end of the needle only around the northerly half of the circumference, while the southern portion of this lower rim attracted the marked end in consequence of lateral induction, as in N. and S. rails.

Thus, upon a comparison of all these facts, it would appear that, if the magnetism induced by the earth is due to so-called currents of electricity, those currents must be underneath the rails, and must move from west to east, under the south to north rails, and from south to north under the west to east laid rails, as indicated by the arrows in the diagram.

This accords perfectly with what we should theoretically expect, in our northern hemisphere, if the electricity in the earth's crust is due to thermo-electrical currents from east to west, namely, from the more heated to the less heated portion, on any given latitude, while the earth revolves from west to east; as well as also from electrical currents trending from tropical to Arctic regions.

As the network of iron rails spreads from year to year more extensively over our continent, it will be interesting to observe whether or not any effect is produced, meteorological, agricultural, etc., by this diffusion of magnetism.

It may further interest some of your readers to have attention called to facts indicating

SYNCHRONOUS SEISMOLOGY.

The year recently closed furnishes interesting corroborative testimony of an apparent law regarding the propagation of earthquake movements most readily along great circles of our globe, as well as evidence that these seismic movements are frequently transmitted along belts (approximating to great circles) coincident sometimes with continental trends, at other times with fissures which emanate in radii at every 30 deg., around the pole of the land hemisphere in Switzerland, as described in one of my papers, read at the Montreal meeting of the A.A.A.S.

The terms synchronism or synchronous, as here used, are not designed to imply absolute simultaneity (although that is sometimes the case with disturbances 180 deg. apart), but are rather intended to indicate the tendency presented by these phenomena to exhibit this internal activity, during successive days, weeks, or even months, along a given great circle of the earth, especially one or more of those connected with the land center; perhaps most of all along the great circle which forms the prime vertical, when the center of land is placed at the zenith.

In order to test the above, let us examine the record of the most prominent earthquakes or volcanic eruptions for the year 1883.

Late in Dec., 1882, and early in Feb., 1883, shocks occurred in New Hampshire; on Jan. 11, 1883, also at Cairo, Illinois, and about the same time at Paducah, Ky.; Feb. 27 at Norwich, Conn., and early in Feb. at Murcia, Spain.

These, by examination of any good globe, will be found on a belt forming one and the same great circle of the earth.

Late in March and during part of April the volcano of Ometeke in Lake Nicaragua was active (after being long dormant); Panama, portions of the U.S. of Colombia, and of Chili; also, in May, Helena, M.T.; and, in June, Quito (with Cotopaxi active) were all more or less shaken by earthquakes; and are all found on one belt of a great circle.

The principal record for the remainder of the year comprised:

An earthquake at Tabreez in North Persia, early in May, 1883.

The awful destruction in Ischia, July 29 (with Vesuvius active).

The fearful eruption in the Straits of Sunda, 25th Aug. and later.

Shocks in Sumatra and at Guayaquil, about same date or early in Sept.

Shocks at Dusseldorf, according to a Berlin paper of 5th Sept.

Shocks at Santa Barbara and Los Angeles, early in Sept.

Shocks at Gibraltar and Anatolia in October.

Shocks at Malta, Trieste, and Asia Minor in October.

Azram shaken late in Sept., and great destruction between Scios and Smyrna.

Lastly, the formation of a new island in the Aleutian Archipelago. Date of outburst, early in October, 1883.

Besides these, there were several other less severe disturbances, the records of which are chiefly obtained from Nature, and which will-be referred to below.

If the globe be so placed as to have the land center at the zenith, the exact position of the new island, near Unnok, will be found under the brazen meridian, while Agram, Tabreez, Sunda, Sumatra, Quito, and Guayaquil are all on the prime vertical.

Vesuvius and Hecla were both active early in the year, and they, with the ever restless Stromboli, are situated on the great circle which forms with the land center at Mount Rosa, the radius running S. 30 deg. E., and which would embrace the chief disturbances up to the middle of the year, including as we go north Malta, Sicily, Rome, region of the Po, Bologna, and in the Western Continent, after passing Hecla, Helena in Montana Territory, reaching in Washington Territory and Oregon the belt of it. American volcanoes: Mounts Baker, Rainier, St. Helens, Hood, and Shasta.

Still another seismic belt, starting from the ever active Fogo, and passing through Teneriffe (at that time erupted), would include the regions disturbed in Oct. and Nov., namely, Cadiz, Gibraltar, Malaga (Murcia and Valencia somewhat earlier); it then traversed the center of land, caused the earthquakes at Olmutz in Moravia, and even tremors felt at Irkutsk, as the seismic war moved along said great circle to the volcanic region of S. Japan.

Again, the belt which covers the meridian of land center (about 8 deg.-10 deg. E. long) covers also the region of a disturbanced area in Norway, as well as that portion of Algeria, viz., Bona, in which a mountain 800 meters high, Naiba, is gradually sinking out of sight. About 100 geo. miles E. of Bona is where Graham's Island appeared in the Mediterranean, and a few months later disappeared in deep water.

Another highly seismic belt extends from the volcanoes of Bourbon, N. Madagascar, and Abyssinia to Santoria and the oft disturbed Scios, Smyrna, and Anatolia region; and along the same great circle were shaken Patra in Greece on the 14th Nov., and Bosnia on the 15th; while shocks had been felt at Trieste and Muelhouse about the 11th, and at Styria on the 7th, and disturbances at Dusseldorf in Sept. Finally, on the 28th Dec. S. Hungary (near the confluence of the Drave with the Danube) was visited by seismic movements along this same great circle, which passes through the extinct volcanic region of the Eifel, the oft shaken Comrie in Perthshire, Scotland, the volcanic Iceland, our National Park with its thousands of geysers, the cataclysmic region of Salt Lake and the Wahsatch Mountains (so graphically described by the geologists of the U.S. Geol. Survey), giving rise in Sept. to the earthquakes of Los Angeles and Santa Barbara, and finally reaching the volcanic islands of the Marquesas group.

Thus the seismic efforts of 1883 may be seen to have expended their force partly along the great backbone of the S. and N. American Cordillera, but more especially from the center of land E. and W. along its prime vertical from Sunda to Quito, also southwesterly by the E. coast of Spain, as well as due S. through Algeria, and S. 30 deg. E. through Rome, Naples, Sicily, etc. Finally, the autumnal catastrophes at and near Scios, Anatolia, etc., seem to have been caused by a seismic wave, propagated along the great circle, which often agitates Janina, and produces earthquakes at Agram, where this great circle crosses the prime vertical.

RICHARD OWEN.

New Harmony, Ind., 27 Feb., 1884.

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THE IRON INDUSTRY IN BRAZIL

(PROVINCE OF MINAS GERAES.)

By Prof. P. FERRAND.

Up to the present time, the methods employed in the province of Minas Geraes (Brazil) for obtaining iron permit of manufacturing it direct from the ore without the intervening process of casting. These methods are two in number:

1. The method by cadinhes (crucibles), which is the simpler and requires but little manipulation, but permits of the production of but a small quantity of metal at a time.

2. The Italian method, a variation of the Catalan, which requires more skill on the part of the workmen and yields more iron than the preceding.

As these methods seem to me of interest, from the standpoint of their simplicity and easy installation, I propose to describe them briefly, in order to give as faithful and general an apercu as possible of their application. At present I shall deal with the first one only, the one called the method by Cadinhes.

STUDY OF THE METHOD BY CADINHES.

The province of Minas Geraes ocupies a vast extent in the empire of Brazil, its superficies being about 900,000 square kilometers, representing nearly a third of the total surface.

The population is relatively small and is disseminated throughout a much broken country, where the means of communication are very few. So it is necessary to succeed in producing what iron is needed by means that are simple and that require but quickly erected works built of such material as may be at hand. The iron ore is found in very great abundance in this region and is very easily mined.

In the center of a mass of quartzites that seem lo constitute the upper level of the eruptive grounds of the province, there are found strata of an ore of iron designated as itabirite—a mixture of oxide of iron and quartz. These strata are of great thickness, and have numerous outcrops that permit of their being worked by quarrying.

These itabirites present themselves under two very distinct aspects and offer a certain difference in their composition. Some are essentially friable, and are called by the vulgar name of jacutingaes. It is this variety (which is the one most easily mined) that is principally consumed in the forges. The others, on the contrary, are compact. Their exploitation is more difficult, and before putting them into the furnaces it is necessary to submit them to breakage and screening; so the use of them is more limited.

The first variety contains less iron and more gangue, but, per contra, possesses much oxide of manganese. The second, on the contrary, is formed almost wholly of oxide of iron with but little gangue and only traces of oxide of manganese. The following are analyses of these two varieties of ore:

Friable Ore.

Fe{2}O{2}.................................. 84.9 Oxide of manganese........................... 9.2 Water........................................ 1.9 Quartz....................................... 4.1 —— 100.1

Compact Ore.

Fe{2}O{3} and traces of manganese.......... 99.6 Quartz....................................... 1.1 —— 100.7

Situation of the Forges.—A forge is usually placed on the bank of a brook, or rather of a torrent, which supplies the fall of water necessary for the motive power by means of a flume about a hundred meters in length. In most cases the forge is surrounded on all sides with a forest which yields the wood necessary for the manufacture of the charcoal, and is in the vicinity of the iron quarry, so as to reduce the expense of hauling the ore as much as possible. The neighboring rocks furnish the foundation stones and stones for the furnaces; the decomposed schist gives the cement and refractory coating, and the forest provides the wood necessary for the construction of the road, sheds, etc. The head of the trip hammer, the anvils, and the tools are the only objects that it is necessary to procure, and even these the master of the forge often manufactures in part, after beginning production with an incomplete set.



General Arrangement of a Forge.—A forge usually consists of one or two furnaces of three or four crucibles (the one shown in plan in Fig. 1 has only one four crucible furnace, A); 1 or 2 two fire reheating furnaces, B; 1 trip hammer, C, actuated by a hydraulic wheel, D; 2 tromps which drive the wind, one of them, E, into the cadinhes (crucibles), and the other, F, into the reheating furnace; 2 anvils, G and H, placed near the furnace, for working delicate pieces; and finally, the different tools that serve for maneuvering the bloom and finishing the bars. The charcoal is preserved from rain under a shed, l. The ore, which is brought in as needed, is dumped in a pile at M, in the vicinity of the crucibles. The buildings are set back against the mountain, and the water is led in by a double flume, L and N, made of planks, and empties on one side into the wheel and into the tromp, F, and on the other into the tromp, E, and then runs into a double waste channel, P and Q, which carries it to the stream.



Four Crucible Furnace (Fig. 2).—The arrangement of a furnace is very simple. It consists of a cube of masonry containing several cylindrical apertures with elliptic bases, whose large axis is paralleled with the smaller side of the masonry. This form recalls that of a crucible; and these cavities are, moreover, so named. In the front part of each cadinhe there is a rectangular aperture that gives access to the bottom of the crucible and facilitates the removal of the bloom therefrom. At the back part there is a small aperture for the introduction of the tuyere, and which permits, besides, of the nozzle of the latter being easily got at so as to see whether the blast is working properly.

The sides of the crucibles are covered with a thin layer of refractory clay, and their bottoms have a spherical concavity to hold the bloom. The tuyere, which is fitted to a wooden conduit of square section that runs along the back of the masonry, is placed in the axis of the cadinhes and enters the masonry at a few centimeters from the bottom in such away that its nozzle comes just flush with the surface of the refractory lining. This arrangement prevents the tuyere from getting befouled by scoriae during the operation of the furnace and thus interfering with the wind.

Tromp.—The tromp which furnishes the necessary wind to the cadinhes consists of a hollow wooden conduit, a (Fig. 3), of square section, which enters a chamber, b, along a length of 0.1 m. This conduit, which is about 7 meters in height, receives the water from the flume through the intermedium of an ajutage of pyramidal form, which serves to choke the vein of liquid, and the extremity of which is at a few centimeters from the conduit in order to facilitate the entrance of the air; the latter being attracted by an ill defined action that is supposed to be due to its being carried along by the water, and to a depression produced by choking the flow of the liquid.



Since the air that is sucked in during the operation has constantly same pressure, there is no valve for regulating the entrance of the water into the vertical conduit. Upon issuing from the latter, the mixture of air and water strikes the surface of the water in the chamber, b, and the violence of the shock upon the bottom is deadened by the interposition of a stone. While the water is escaping through a lateral aperture in the chamber, b, the air is reaching the tuyeres through a wooden conduit of square section which is fitted to an aperture in the upper part of the chamber. This sorry arrangement, which obliges the mixture of air and water to penetrate the water at the bottom of the upright conduit, a, retards the separation of the two fluids, and results in damp air being forced into the crucibles.

The Trip Hammer.—Fig. 4 shows the general arrangement of the apparatus that go to make up the forging mill. The hammer and cam shaft have their axes parallel, and the latter is placed in the prolongation of the axis of the wheel. The hammer consists of a roughly squared beam, 4 meters in length, and of 0.25 m. section. The head, A, consists of a mass of iron weighing 150 kilos, including the weight of the straps that surround the beam on every side of the piece of iron. The axis of rotation is situated at the other extremity of the beam, B. The cam shaft which serves to maneuver the trip hammer is provided with four cams which lift the beam at a point near the hammer. The length of this shaft (to the extremity of which is adapted the water wheel) is 4.75 m., and its diameter is 0.50 m. The wheel is an overshot one, 3.25 m. in diameter by 1 m. in width. The water, which is led to it by a flume, acts upon it by its weight and impact, and is retained in the buckets and kept from overshooting the mark by a jacket made of planks.



The anvil upon which the hammer strikes is surrounded by a bed of stones (quartzites) derived from the neighboring rocks. It is a mass of iron, 75 kilogrammes in weight. In order to prevent vibrations in the trip hammer when it is lifted, and increase the number of blows, there is established a spring beam, which is formed of unsquared timber, which is firmly fastened at one of its extremities, and which receives at the other end the shock of the hammer head when the latter reaches the end of its upward travel.

Reheating Furnace.—This is a double fire furnace, like those used in our smithies, except that the wind, instead of being forced into it by means of a bellows, is supplied by a tromp which receives water from the same channel as the wheel. The two furnace tuyeres are arranged exactly like those of the cadinhes, upon a wooden conduit which starts from the wind chamber (Fig. 5). This furnace serves to prevent the cooling of such blooms as are awaiting their turn to be shingled, and of such bars of finished iron as are being made into tools.

OPERATION OF THE SYSTEM.

A forge like the one whose plan we give, may be run with 1 workman at the cadinhes, 1 assistant, 1 workman at the hammer; total, 3 men.

Furnace.—The work lasts about twelve hours per day, and three operations of three to four hours are performed in each cadinhe, thus making twelve per day. At each operation, 22.5 kilos. of ore and 45 of charcoal are used. From this there is obtained a bloom of 15 kilos. The operation is performed as follows:

While the assistant has gone to put the bloom of the preceding operation under the hammer, the workman prepares at the bottom of the crucible a bed consisting of a mixture of sand and very fine charcoal, and then fills the crucible up to its edge with charcoal. At the end of a quarter of an hour, the fuel being thoroughly aglow, the workman puts in the first charge of ore in powder (jacutingue), about 2 kilos, and covers it with charcoal.

Starting from this moment, he goes on charging every five or ten minutes with 1.5 to 2 kilos of ore, taking care in doing so to keep the crucible stuffed with charcoal, which the assistant places in piles around each cadinhe. This lasts about two and one-half hours. At the end of this time he stops putting in charcoal, and standing upon the masonry, walks from one cadinhe to another, carrying a large rod, in order to study the lay of the bloom. Then, the fire being entirely out, he scrapes out the bed of sand and charcoal that closes the opening in the bottom of the crucible, removes the mass of ferruginous scoriae which forms a hard paste and surrounds the bloom, and takes this latter out by means of a hook.

The workman runs the four cadinhes at once, this being easily enough done, since he has neither to bother himself with regulating the wind, which enters always with the same pressure, nor with the flow of the scoriae, which remain always at the bottom of the crucible. His role consists simply in keeping his fires running properly, being guided in this by the color of the flame without making an examination in the interior. He draws each of the four blooms out from its bed at the end of the operation, while the assistant carries the first to the hammer and the three others to the reheating furnace. He afterward cleans out the crucible, prepares the bed of sand and charcoal, fills with charcoal, and then passes to the next, and so on.



Trip Hammer.—The workman at the hammer takes the bloom from the hands of the assistant and shingles it under the head. Then he begins to give it shape, bringing it to the state shown at c, in Fig. 7. The assistant then brings him another bloom and takes the one that has been shingled to the reheating furnace, where he heats but one of its extremities. When the four blooms have been shingled, the workman takes up the first and begins to draw out one of its extremities, which he afterward cools in water and uses as a handle for finishing the work, d. Then he reheats the other extremity, and, after drawing it out as he did the other, obtains a bar of finished iron which he doubles, as shown at e, to thus deliver to the trade.



One of these bars weighs from 11 to 12 kilogrammes. It will be seen that, during the course of the work, the furnace workmen and the hammer workmen have well defined duties to perform; but it is not the same with the assistant, who goes from one to the other according to requirements. There are, however, some forges in which each of the workmen has an assistant, since the blooms produced are heavier, and one assistant would not suffice for the work of the two men. In such a case the assistant at the crucibles carries the blooms to the reheating furnace, and the assistant at the hammer carries them from thence to the hammer.



ELABORATION OF THE ORE.

We have seen that the workman who has charge of the fire contents himself with putting charcoal and ore alternately into the crucibles, and that too according to the aspect of the flames, without making any examination in the interior, in order to judge whether the work is proceeding well. The bloom forms gradually beneath the nozzle of the tuyere, in the center of the bed of sand and charcoal, and is surrounded on every side with an exceedingly pasty mass, formed of silicates of iron and manganese (Fig. 7). It is only at the end of the operation that the workman, by means of a rod, causes the burning coal to drop and verifies the proper position of the bloom by breaking the layer of scoriae that surrounds it. This coating he breaks off, removes the bloom with a hook, and agglutinates with his rod the different bubbles that it exhibits, and the assistant then carries it to the hammer.

SETTING UP A FORGE.—SELLING PRICE OF THE IRON.

To set up a forge like the one we have described, it is necessary to count upon a first cost of about 10,000 francs. Add to this the cost of 50 hectares of forest to furnish the charcoal that the workmen have to make every day. The cost of this is very variable, and floats between 2,500 and 5,000 francs per 100 hectares. The cost the ore is only that connected with getting it but and hauling it.

Manual Labor.—The charcoal burners receive 1.25 francs per load of 90 kilos, thus bringing the price of the product (including cost price of forest) at 2.4 francs per 100 kilos. The workmen in the furnace are paid at the rate of from 2.50 to 3.75 francs per day. Those that work the hammers receive 3.75 francs, and the assistants 1.25 francs.

Carriage of the Forged Iron.—The iron is carried from the forge to the places of consumption on the backs of mules, and the cost of carriage is, on an average, 0.25 franc per 100 kilos and per kilometer.

Selling Price.—The selling price is very variable, and depends principally upon the distance of the place where sold from the different forges that surround it. At Ouro Preto the price varies between 45 and 50 francs per 100 kilos.

The following is a resume of the data which precede:

Cost of first establishment.................. 10,000 fr. Charcoal per kilogramme...................... 2.40 { Furnace men.... 2.50 to 3.75 Manual labor per day { Hammer men............. 3.75 { Assistants............. 1.25 Carriage of forged iron per kilometric ton..... 2.50 Selling price per 100 kilos................ 45 to 50

—Le Genie Civil.

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THE STEAMER CHURCHILL.

We give engravings of the Churchill, a vessel lately built to the order of Mr. Walter Peace, London agent to the Natal Harbor Board, by Messrs. Hall, Russell, and Co., Aberdeen. She was designed by Mr. J.F. Flannery, consulting engineer to the Board, for special service at Natal. The Churchill has been constructed so as to be capable of towing into or out of harbor over the bar in any weather, of acting as a very powerful fire engine, of carrying a large amount of fresh water for the use of other ships, of landing troops from transports which the harbor is too shallow to admit, of recovering lost anchors and cables, of which there are a large number off the coast, and of acting in time of need as a torpedo or coast defense vessel; she was launched on the 16th August, and is likely to fulfill all these requirements.



The principal dimensions of the vessel are: Length between perpendiculars 115 feet, breadth, extreme, 22 feet, depth of hold 11 feet, and maximum draught with full bunkers 7 feet 6 inches. There are four water-tight iron bulkheads forming five compartments; the stern is built very full to protect the propellers. Accommodation is arranged on deck for the captain aft with two spare berths, mate and two engineers amidships, while six white hands will occupy the forward forecastle, and six Kaffirs the after one. For towing purposes she is fitted with one main and two skip hooks secured to the main framing; towing rails are placed aft, while bitts are put on one each quarter, will be seen by referring to the deck plan.

The vessel is propelled by twin screws 6 feet 8 inches in diameter and 13 feet 6 inches pitch; these are of cast iron, have four blades, and are driven by a double pair of compound inverted direct acting engines (see Figs. 4 to 7) which are capable of developing 600 indicated horse power, and whose cylinders are 19 inches and 34 inches in diameter with a stroke of 2 feet. The condensers form part of the engine frame, and have guide faces cast on for the crosshead shoes. They are fitted with gun metal tube-plates, and each contain 516 tubes, 3/4 inch in diameter, which have an exposed length of 6 feet 5 inches, and give a total cooling surface of 650 square feet. The air and circulating pumps are bolted to the back of the condensers, and are worked by levers from the engine crosshead. Each engine has one feed and one bilge pump attached to the air pump, and worked by the same lever. The plan of the engines shows the pump arrangement very completely.



The steam is supplied by two circular return tube boilers, 9 feet 6 inches in diameter and 10 feet long, with two furnaces in each. The boilers, which are of steel throughout, except the tubes, are placed longitudinally, and are fitted with two pairs of the Martyn-Roberts patent safety valves. They have one steam dome between them. The total heating surface is 1,700 square feet, the total steam space is 330 cubic feet, and the working pressure 100 lb. per square inch.

The fire pump is a Wilson's "Excelsior," with 10 inch steam cylinder and 8 inch water barrel. This powerful pump is in a special compartment of the fore hold, and will draw water from the bilge, sea, or either hold. A steam windlass and a double-handle winch are on deck as shown. On trial trip the engines of the Churchill indicated a maximum of 645.5 horse power, driving the vessel 10.495 knots per hour. The vessel is remarkable for diversity of uses, for heavy engine power in a small hull, and for general compactness of arrangement.—Engineering.

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THREE-WAY TUNNELS.

Mr. T.R. Cramton, who at the Southampton meeting of the British Association suggested a method of tunneling which, under certain conditions, seems of excellent promise, brought forward a suggestion at Southport for the construction of three-way tunnels. Now, the undoubted aim of all engineers is economy of construction and the securing of permanent advantages. Mr. Crampton maintains that the suggested system will give these, that three tunnels of, say, 17 ft. diameter, can be constructed cheaper than one of 30 ft. diameter. After describing Sir J. C. Hawkshaw's scheme for the ventilation of long tunnels, the three-way scheme was discussed. Three separate tunnels of 17 ft. diameter each, or 227 ft. area, are to be connected by large passages about midway of their length. These passages are without valves; in fact, free air passages. Between these midway connections and the ends, say again midway between, is formed a branch at right angles either above or below with separate openings from the branch into the other tunnels, such openings being provided with doors or valves quite clear of the main tunnel, any two of which may be closed, thus separating at this point the corresponding tunnels from the third. The branch is to be led to any convenient position where the exhustion apparatus can be placed. If two of the tunnels are left open to this branch, and the third one shut off from it by closing the doors, the vitiated air will be drawn from the two working tunnels, through the connecting branch, while fresh air will be partly sucked down the vertical shafts through their open ends and partly at the center tunnel, which is supplied by forcing air down the vertical shaft in communication with it, a stop or door being placed just outside of the bottom of the shaft so as to compel the air to flow to the center of the tunnel. It will be observed that no trains are running in this air tunnel so long as it is so used; there are similar doors for the working tunnel, but they are kept open, unless either of them is required to be made into an air tunnel, so that the passing trains run no risk of running into the doors. By means of the doors above mentioned, any one of the three tunnels can be used as a fresh-air tunnel, in which the men doing the repairs to the road would be clear of the traffic, while the other two are used for the traffic, as well as outlets for the mixed impure gas and air. If a breakdown of a train occurs in any one tunnel, that tunnel can at once be converted into a fresh-air one, while its traffic is transferred to the one previously used for air, thereby avoiding delay. The system described for splitting the air and drawing off the noxious gases is very similar to that described by Mr. Hawkshaw at Southampton. The valves and other details being added, to make the system applicable to three tunnels, it will be obvious that other modes of ventilation may be adopted. In order to reduce the number of men working in the tunnel it is proposed, if found practicable, not to adopt the ordinary ballast and cross sleepers, but to substitute the longitudinal timber system, the timbers to be secured to brickwork or concrete, forming a part of the tunnel lining, placing efficient elastic material between the foundation and longitudinals for their whole area, also between the rails and sleepers. An open drain is formed between the rails; by this plan any water accumulating flows over smooth surfaces through small channels into a drain, the tunnel on each side being dry. The saving of labor in repairs, if this system can be employed, is so evident that a large amount of money might be expended in endeavoring to discover a suitable elastic material for the purpose. There are data on many long viaducts sufficient to justify experiments being made on the subject, and it is not unreasonable to expect that suitable material may be met with. In very long tunnels nothing should be omitted tending to reduce the number of men working in them. The opinion was expressed that in tunnels passing through solid materials, and proper foundations being made for the longitudinals to rest upon, with good elastic material placed between the rails and sleepers and foundations, one-half of the men employed on the ordinary cross sleeper road resting on ballast would be saved, more particularly as the repairs are effected in pure air free from the traffic as explained. The estimate as to the cost of this system was upon the dimensions given by Sir J. Hawkshaw, and the following gives the comparison:

The quantity of excavation and brickwork or concrete in each case will be as follows: Single tunnel: 30 ft. diameter lining, 3 ft. thick, with the brickwork forming the air passage = to 36.5 cubic yards per yard forward. Excavation to outside of brickwork 36 ft. diameter = to 113 cubic yards per yard forward. Three tunnels 17 ft. diameter and 18 in. brickwork. Brickwork lining for three tunnels = 24.5 cubic yards per yard forward. Excavation outside brickwork for the same 105 cubic yards per yard forward. It is assumed that three 17 ft. tunnels are stronger, more conveniently formed, and involve less risks in construction than one of 30 ft. diameter; at the same time there is no difficulty in making the latter. The above shows the saving in the three tunnels of 23 per cent. in brickwork, and about 7 per cent. of earthwork, compared with one of 30 ft. With regard to ventilation, it is well known that the power required to force air along passages is practically as the cube of the velocity; and as the area of the air passages in the single tunnel is 106 ft. with speed ten miles per hour, and that of one of the 17 ft. diameter is 227 ft., or rather more than double, giving only five miles per hour velocity, it follows that the power for this portion would be eight times less. That for the working tunnels would be practically the same, the velocities being nearly alike in both cases, which would be about 21/2 miles per hour—the 30 ft. having an area of 470 ft., the two single ones together about 450 ft. Upon the face of it the system deserves a trial. A full consideration of the scheme by engineers preparing plans for new tunnels would no doubt throw further light upon the subject and be of interest wherever such work is contemplated.—Contract Journal.

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MONT ST. MICHEL.

Every one who has the slightest regard for historical monuments, who values mediaeval architecture, or cares in the least degree for the beautiful and the picturesque, must heartily sympathize with M. Victor Hugo in his protest against the proposed scheme for uniting the wonderful island of Mont St. Michel with the mainland by means of a causeway, and possibly a railway!

Those who know Mont St. Michel well, and, like the writer, have spent several days upon the island, cannot but feel that such a scheme would not only be a frightful disfigurement, but would entirely destroy all the associations and the poetry of the place. Practical people will say, "Modern improvement cannot stop in its march forward to consider poetical associations and mere artistic whims and fancies." Now, this would be a possible argument if Mont St. Michel were a busy, thriving town, a commercial port, or the seat of great industries; but in a case where the only trade is that of touting, the only visitors sightseers, the only "stock-in-trade" mediaeval remains, surely, from a practical point of view, anything which will injure these antiquities will really destroy the importance of the island, as its only value consists in its wonderful historic and artistic associations.



The first glimpse of Mont St. Michel is strange and weird in the extreme. A vast ghostlike object of a very pale pinkish hue suddenly rises out of the bay, and one's first impression is that one has been reading the "Arabian Nights," and that here is one of those fairy palaces which will fly off, or gradually fade away, or sink bodily through the water. Its solemn isolation, its unearthly color, and its flamelike outline fill the mind with astonishment.

Mont St. Michel is by far the most perfect example of a mediaeval fortified abbey in existence, with its surrounding town and dependencies, all quite perfect; just, in fact, as if time had stood still with them since the fifteenth century. The great granite rock rises to the height of two hundred and thirty feet out of the bay; it is twice an island and twice a peninsula in the course of twenty-four hours. The only approach is at low water, by driving or walking across the sands. When, however, one arrives within a few yards of the solitary gate to the "town," walking or driving has to be abandoned, and here the commercial industries of the inhabitants commence. A number of individuals, half sailors and half fishermen, are standing ready to carry you on their shoulders over the small gully, which is very rarely quite dry. Entering through the old gate one sees two ancient pieces of cannon taken from the English, who unsuccessfully laid siege to the place in 1422. Close to the gate are the two rival inns, which are very primitive in their arrangement, the entrance hall forming the kitchen, as in many old Breton houses. A second frowning old gateway leads to the single street, which, passing between two rows of antique gabled houses, and under the chancel of the little parish church, conducts one to the almost interminable flight of stone steps leading to the gateway of the monastery. Upon ringing the bell a polite lay brother opens the iron-studded door, and we are admitted into a solemn, vaulted hall, with another stone staircase opposite. Here we go up and up, to a second vaulted hall, where, in olden times, we should have had to give up any arms which we were carrying. Then another stone staircase, which lands us in a small court with a well in it, at the opposite end of which is a heavy and solid arched doorway. We pass through this, expecting to find ourselves on the top of the central tower of the church at least, and are surprised to find ourselves in the solemn and almost dark crypt of the church. Here we have climbed up some 230 feet above the world and the sea to find ourselves in an underground vault; up in the air and down under the rock at the same time. Wonderfully beautiful is this strange crypt, when one's eye gets accustomed to the gloom, with its exquisite ribbed and vaulted roof, supported upon huge circular columns. Returning to the court, another doorway conducts us into a most superb Gothic hall, with a row of slender columns down the center. This was the monks' refectory in ancient times; adjoining this is another grand hall, divided into four aisles by rows of granite columns, all of the most perfect thirteenth century work. Above these are two other halls, still more magnificent than those below. One of these, called the "Salle des Chevaliers," is probably the most beautiful Gothic hall in existence. Again a flight of stone stairs, and we find ourselves, where we should certainly not have expected, in the cloisters of the monastery, the exquisite architecture of which, with its countless marble columns and delicate double arcades, cannot be described.

The church deserves a few words, as it is a veritable cathedral as to size and grandeur. The choir is immensely lofty, and constructed of granite most elaborately wrought in the later Gothic or flamboyant style. The nave and transepts are in the old Romanesque style, with solid pillars and low round arches. The church is beautifully kept, and contains some very interesting old reredoses and altars with carving in alabaster. The one modern altar in the Lady Chapel is composed entirely of silver! Our space will not permit us to describe the numerous interesting old Abbey buildings—the library, the prior's lodging, the vast kitchen, the prisons, the dungeons, and the means of supplying the place in times of siege. The proposed causeway would join the island to the left of our view, and our readers can imagine the abominable effect of a high embankment disfiguring this point, and breaking through the interesting old walls and towers, with, perhaps, a Brummagem Gothic station against the old time-worn gateway.—H. W. Brewer, in London Graphic.

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ADORNMENTS OF THE NEW POST OFFICE AT LEIPZIG.

The cuts given herewith, taken from the Illustrirte Zeitung, represent two statues for the new Post Office at Leipzig. The sculptor, Kaffsack, has represented the post and the telegraph as winged female figures. The figure representing Mail holds a horn or trumpet in her left hand, and a letter in her right hand. The figure representing Telegraphy holds a bunch of thunderbolts in her left hand, and unrolls a band for receiving dispatches with her right hand. It will be observed that the figure representing Telegraphy is made much lighter and more graceful than the figure representing Mail, and has also a more energetic expression of countenance, thus indicating the greater speed of Telegraphy.



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COAL GAS AS A LABOR-SAVING AGENT IN MECHANICAL TRADES.

By THOMAS FLETCHER, F.C.S.

Gas, as a fuel, is an absolute necessity to the economical carrying out of many commercial processes. It is often used in the crudest and most costly way; a burner may be perfect for one purpose, yet exceedingly wasteful for another, and however good it may be, an error of judgment in its application may lead to its total condemnation. An excess of chimney draught, in cases where a flue is necessary, may pull in sufficient excess of cold air to almost neutralize the whole power of the burner, unless a damper is used with judgment. With solid fuel, an excess of draught causes more fuel to be burnt, but with gas the fuel is adjusted and limited; there is no margin or store of fuel ready to combine with the excess of air, which, therefore, lowers the amount of work done by its cooling power. The power of any burner, for any specified purpose, depends not only on its perfection, but to a far greater extent on the difference in the temperature of the flame and of the object to be heated. For instance, if a bright red heat is required, it is not possible to obtain this temperature economically with any burner working without an artificial blast of air; the difference between the temperature of the flame and that of the object heated is too little to enable the heat to be taken up freely or quickly, and the result is a large loss of costly fuel. If we want to obtain high temperatures economically, an artificial blast of air is necessary, and the heavier the pressure of air, the greater the economy. On the contrary, low temperatures and diffused heat are obtained best by flames without any artificial air supply.

For such purposes as ovens, disinfecting chambers, japanners' stoves, founders' core drying, and similar requirements the best results are obtained by a number of separate jets of flame at the lowest part of the inclosed space, and the use of either illuminating or blue flames is a matter of no importance, as the total amount of heated air from either character of flame is the same. If there is any preference, it may be given to illuminating flames, as the proportion of radiant heat is greater, and this makes the average temperature of the inclosed space more equal; but on the other hand, may be considered the greater liability of the very fine holes, necessary for illuminating flames, to be choked with dust and dirt. This may, to a great exent, be obviated by using very small union jets, and setting them horizontally, so as to make a flat horizontal sheet of flame. Burners placed this way are practically safe from the interference of falling dust or dirt, but not from splashes. Falling dirt or splashes must always be considered in the arrangement of any burners, and the ventilation must be no greater than is absolutely necessary for the required work. In cooking, this limit of ventilation may be exceeded, as most things are better cooked with a free ventilation, the extra cost of fuel being well compensated for by the better quality of the result.

The air in an oven or inclosed space heated by flames inside is similar in character to highly superheated steam. It contains a large proportion of moisture, and yet has the power of drying any substance which is heated to near its own temperature. A mass of cold metal placed in the oven is instantly bedewed with moisture, which dries up as the temperature of the metal rises. This is, for many purposes, an objection, and the remedy is to close the bottom of the oven and place burners underneath. If for drying purposes and a current of air is necessary, the simplest way is to place in the bottom of oven the a number of tubes hanging downward in such a position that the heat of the flame acts both on the bottom of the oven and the sides of the tubes, which, of course, must be long enough for the lower opening to be well below the level of the flame. The exit may be at any level, but for drying purposes it is better at the top, and it should be controlled by a damper to prevent cooling by excessive currents of air. If not otherwise objectionable, the arrangement of flames inside the oven is far the most economical in use.

Where an oven or drying chamber is used continuously, it should be jacketed with slag wool or boiler composition, but for many purposes this is no advantage. As an example both ways, I will instance the drying of founders' cores where there is only one blow per day. The cores of an ordinary foundry can be dried by gas in a common sheet iron even in about half an hour; any accumulation of heat after that time would be useless, and a jacketed oven would be of no advantage.

For the disinfection of clothes in vagrant wards and hospitals for infectious diseases, on the contrary, a continued heat is necessary, and in this case the accumulation of reserve heat, which takes place slowly in a jacketed oven, becomes of value, as the gas can be turned low or out, and the ventilators closed, insuring a more complete disinfection with a much smaller gas consumption. Where an oven or heated chamber is much used for periods of over half an hour at once, a non-conducting casing pays well by reduced gas consumption.

For albumen and glue drying, leather enameling, tobacco drying, and purposes where a large space has to be very slightly and equally warmed when the weather is unfavorable, steam-pipes are generally used, but, not being always available, an exceedingly good arrangement may be made by placing at intervals in the room gas burners, of any construction, close to the floor, and surrounded with a sheet-iron cylinder, say 2 ft. or 3 ft. high. The top of these cylinders must be connected throughout with a fairly large flue, which will take the products of combustion from the whole, and this flue must be carried either horizontally, or with a slight rise, so as to utilize all the waste heat. The reason for having a number of stoves at intervals is that the heat in a flue will not carry, for any useful purpose, more than about 8 ft. or 10 ft., and a single stove would give an irregular temperature in any except a very small room. If all are not used at once, the flues of those not in use may be closed by a damper to prevent down draught. The use of hot water pipes heated by gas may also be occasionally advisable, but, unless for some special reason, it is much more economical to use coal or coke, as the bulk of water makes an exceedingly good regulator, and makes a fire practically as steady and reliable as gas, thus superseding the more costly fuel.

For one of my own purposes I need hot-water pipes, having very little variation in temperature night and day; and using coke for economy's sake, I get a regular temperature by heating a large quantity of water, about 200 gallons, with the fire, and inclosing this in a tank jacketed with slag wool. My circulating pipes run from this tank, and a practically steady temperature, night and day, can be obtained with the most irregular firing, and occasional extinction of the fire for several hours at once.

For the heating of liquids, the greatest economy is to be obtained from one single flame, of as high a temperature as can conveniently be obtained, and the flame must be in actual contact with the vessel to be heated. In jacketing vessels, to prevent draughts, care must be taken that the jackets do not cause currents of cold air to rise rapidly up the sides of the vessel, and so cool it. If this is the case, the use of a jacket, instead of being an economy, is a positive expense, and waste of heat. Many processes, such as making oil and turpentine varnishes, require a heat under instant control, and in these the use of gas is an important matter, as the loss and risk of fire are very serious elements of expense, more especially in small works where special and costly preparations for contingencies cannot be afforded. I have here a burner which, for its power, is, perhaps, the most compact and gives the highest temperature of any burner yet known, and it is easily made in almost any size; it has, I think, many special advantages. The use of gauze, which is its only weak point, is more than compensated for by the very high duties obtained in practice with it, owing to the compactness and concentration of the heat obtained. The following extract from my communication to the Gas Institute will give all particulars as to the constructive detail of this burner. Those who wish to go further into the matter will find the paper referred to in the publication of the Gas Institute for the current year, and also in the Journal of Gas Lighting, June 26, 1883, and the Review of Gas and Water Engineering, June 16, 1883.

"The first and most important part is the mixing chamber or tube, one end of which is supplied separately with gas and air, which at the other end are, or should be, delivered as a perfect mixture. It may be taken as a rule that this tube, if horizontal, should not be less in length than four and a half times or more than six times its diameter. It is a common practice to diminish or make conical-shaped tubes. All my experience goes to prove that, excepting a very trifling allowance for friction, the area of the smallest part of the tube rules the power, the value of the mixing-tube being no more than that of the smallest part. If the mixing-tube is upright, new sources of interference comes in; notably the varying specific gravity of the mixture. Except with one definite gas supply, the result is always more or less imperfect, and regular proportions cannot be obtained. This is now so well known that the upright form has been practically discarded for many years, and is now only used where the peculiar necessities of the case give some special advantage.



"The diameter of the mixing tube is a matter of importance, as it rules the quantity of gas which can be satisfactorily burnt in any arrangement. With large flames, given a certain size of gas-jet, the diameter of the mixing-tube should be not less than ten times as great. For instance, at 1 inch pressure, a jet having a bore of 1/8 inch will pass about 20 cubic feet of gas per hour. To burn this quantity of gas, a mixing tube is necessary 10/8 or 11/4 inch in diameter. By the first rule this tube must be in length equal to four and a half times its diameter, or 5-5/8 inches. It would appear that the mixing-tube, having 100 times the area of the gas jet, is out of all proportion to the size necessary for obtaining a mixture of one of gas to nine or ten of air; but it must be remembered that the gas is supplied under pressure. It is therefore evident that no mere calculation of areas can be taken, into account, unless the difference in pressure of the supply is also considered. A complete reversal of this law is shown in that ruling the construction of blowpipes, which I have already given in a previous paper on 'The Use and Construction of the Blowpipe.' In these the air supply, being under a heavier pressure, is much smaller in area than the gas inlet; and, to obtain maximum power, the air-jet requires to be enlarged in proportion to the gas pressure.

"Given a certain area of tube delivering a combustible mixture, the outlet for this mixture must be neither more nor less than the size of the tube. Taking an ordinary drilled tube, such as is commonly made, and of the dimensions before given—i. e., 11/4 inch bore—if the holes are drilled 1/8 inch in diameter the tube will supply 10 x 10 = 100 of these holes. In practice this rule may be modified.

"The variations from the rule, however, must be a matter of experience with each form of burner. There is also the fact that with small divided flames it is not necessary to mix so large a proportion of air, as each flame will take up air, on its external surface; but in this case the flames are longer, hollow, and of lower temperature. As a matter of actual practice, where a burner is used which gives a number of flames or jets, the diameter of the mixing-tube does not need to exceed eight times the diameter of the gas jet; the remainder of the air required being taken up by the surfaces of the flames.

"Wire gauze, made of wire the thickness of 22 iron wire gauge, 20 wires to the linear inch, and tinned after weaving, has an area in the holes of 1/4 its surface. By calculation, the area of a gauze surface in a burner should, therefore, be taken at four times that of the tube, and our standard of 11/4 inch tube requires a gauze surface of 21/2 inches in diameter. This rule is subject to variation in burners of a small size, owing to the air that can, if required, be taken up by the external surface of the flame, which, of course, is much greater in proportion in a small flame than in a large one. Where the diameter of the gauze is, say, not over one or two inches, the theoretical maximum gas supply may be exceeded, and a varying compensation is necessary with each size. My rule is intended to apply to burners of larger diameters, where the external air supply plays a comparatively unimportant part.



"It must be remembered that burners of this class, which burn without the necessity of an external air supply in a flame which is solid, require the mixture to be correct in proportions. A very slight variation makes an imperfect flame. Not only does the gas jet require to be adjusted with great precision, but it also needs more or less adjustment for different qualities of gas. An ordinary hollow or divided flame is able to take up on its surface any deficiency of air supply; but with the high power solid flames the outside surface is small, and the consequence is that one of these burners, adjusted for gas of poor quality, may, when used with rich gas, give a long hollow or smoky flame, unless the gas jet be reduced in size. When perfect, the flame shows a film of green on the surface of the gauze; and if a richer gas is used, the green film lifts away. To cause this to fall again, and to produce a solid flame, it is necessary to take out the gas jet, and tap the end with a hammer until, on trial, it is found correct. If too small, the green film lies so closely as to make the gauze red hot. Where the 'tailing up' of the carbonic oxide flame is objectionable, there is no practical difficulty whatever in constructing these burners as a ring, with an air supply in the center, which greatly reduces the length of the 'tail.' In practice it is a decided advantage to have a center air-way in all burners of more than about 2 in. diameter, as it enables the injecting tube to be slightly shortened, and lessens the liability of the green film to lift with varying qualities of gas. In this class of burner I have adopted the small central air-way as a decided improvement in the burners."

In such processes as the roasting of coffee, chiccory, grain, etc., a diffused heat is necessary, but of much greater intensity than can be obtained with economy from heated air. In these cases the application of a direct flame is necessary, and it may be in actual contact with the substances to be heated, provided these are kept in constant and rapid motion.

The use of a revolving cylinder brings in complications with any burner which is supplied with gas at ordinary pressures without any artificial air supply, as the currents of air caused by the motion of the cylinder interfere with the satisfactory working of any burner; and the air supply must be either protected from draughts and irregular air currents, or the air must be applied artificially from some independent source. One exceedingly good way of making any burner work, independently of the currents caused by a revolving cylinder, is to apply the flame inside the cylinder at the center, making the substances to be heated to fall in a continuous stream through the flame. This system is not applicable to fine powders or sticky substances, as it necessitates the perforation of the cylinder, to allow of the escape of products of combustion.

For this class of work, a very concentrated heat is not desirable, as a rule, and a slit or a perforated burner is preferable. Of this class of burner I have here a sample, which is not only new in its constructive details, but has great and special advantages for many purposes. As you see, it resembles a number of ordinary furnace bars, with this difference, that each bar is a burner; in fact, it is an ordinary furnace grate, which supplies its own fuel. With the usual day pressure of gas=1 inch of water, this burner will, at its maximum power, consume about 100 cubic feet of gas per hour per square foot of burner surface, and as it can readily be made almost any form or size, its adaptability for a great number of uses is evident. I have made it in many sizes and shapes, to give flames from 1/2 inch wide by 5 feet long to large square or oblong blocks. By applying a blast of air at the ordinary gas jets, and supplying the gas by a separate pipe, or series of pipes, below the open end of the burner, this can be converted into a furnace of extraordinary power. It is quite possible to burn as much as 2,000 cubic feet of gas per hour per square foot of burner surface, producing a heat sufficient to fuse any ordinary crucible. You see its power when I place a bundle of iron wire in the flame; it is, in fact, a concentration of hundreds or thousands of powerful blowpipe flames in one mass. It has also this advantage, that with a blast of air it will burn and work equally well any side up, and the flames can therefore be directed straight on their work without loss. It is, in one form or another, almost a universal burner, as it can be readily adapted to almost any purpose, from tempering a row of needles to making steam for a 200 horse power steam engine. It is easy to make, easy to manage, practically indestructible, and for commercial purposes has, I think, a general adaptability which will bring it, in one form or another, into almost universal use. I may say that when we are in a special fix, this has in every case landed us out of the difficulty.

For heating large plates of metal equally, for drying paper impressions for stereotypers, hot pressing hosiery, crumpet baking, working up plastic masses which can only be worked hot, and work of this class, a number of separate flames equally diffused under the whole surface of the plate are necessary to equalize the heat, unless the plate is very thick, and these are better if produced by a mixture of gas and air; but in heating wide plates one difficulty must always be remembered, the burnt gases from the center flames can only escape by passing over the outer flames, and therefore a space must be left between the top of the flame and the plate, or the outer flames will be smothered and make a most offensive smell.

In hosiery presses, printers' arming presses, and many others, the top plate also requires to be heated. The best way to do this is to use a number of blowpipe flames directed downward. In many cases the supply of air under pressure is a practical difficulty and objection. This is overcome, to a certain extent, by the use of a thick upper plate with a number of horizontal holes, into which a Bunsen flame is directed. In every case I have seen, without one single exception, the holes are either too small, or the burner is placed too close, and the consequence is that the gas, instead of burning inside the holes, as it should, passes through partially unburnt, and is consumed at the opposite end, where it is absolutely useless, the flame not being in contact with or under the surface to be heated, and therefore doing no work. In hosiery presses this is a great objection, as the holes are so long that an equal heat is simply impossible, and the only remedy is to use a blowpipe flame, which forces sufficient air in with the gas to insure combustion where the heat is necessary. The same remark applies to crape and embossing rollers.

For the production of heat in confined spaces and difficult position, the use of an artificial blast of air is becoming an acknowledged necessity, and the small Roots blowers now made for such purposes, and driven by power, are coming rapidly into use.

Sometimes a plate is required to be heated to a high temperature in one confined spot, and, as an example of this, I may take the bluing of the hands of watches. For this purpose I have made several arrangements, and perhaps the best is a thin copper plate, bent down at one side to a right angle. In this angle, underneath, is directed a very fine blowpipe flame on one spot, and the hands are passed singly over this spot until the color comes, when they are instantly pushed over the edge. I have here the arrangement which is generally used for this purpose. For the bluing of clock hands, a larger and more equally heated surface is required, and this can be obtained by a small powerful burner without a blast of air, using a rather thicker plate to equalize the heat. The same arrangement may be used with advantage for tempering small cutters for ornamental turning, penknife-blades, etc., and in these cases the cooler part of the plate is of great value, as it enables the thicker parts to be slowly and equally heated up; the application of a mechanical arrangement to pass the articles to be heated in a regular succession is a matter easily managed.



Among other things which have several times come under my notice may be mentioned cremation furnaces, but I have not yet met, with, or been able to devise, any burner for ordinary coal gas which has worked satisfactorily. This fuel is apparently unfitted for the work, and the best arrangement I know is a number of pipes delivering ordinary "producer" gas from the Wilson or Dowson generators, in exactly the same way as is at present used for firing horizontal steam boilers. For heating book finishers' tools, a ring-flame is the simplest, the tools being supported a little distance above the flame; the usual plan of heating a plate, and placing the ends of the tools on this, necessitates at least double the gas consumption as compared with an open flame. For type-founding machines, bullet moulding, stereotype metal melting, solder making, lead melting, etc., one burner, or rather one flame, should be used of a suitable power for the work, and this should be as perfect and of as high a temperature as possible to insure economy. It is now a simple matter, owing to recent researches in the theory of heating burners, to obtain flames of any power without practical limit, which, without any artificial air supply, will do all which is necessary in this class of work, and the required arrangements are exceedingly simple. With these trades may be classed, also, the concentration and distillation of acids and liquids boiling at a high temperature, and we may also include baths for tinning small articles, and the tinning by fusion of sheet copper, the same burners being applicable, and perfectly suited to all these requirements, unless the tinning baths are long and narrow, in which case the furnace-bar burners again come to the front as the best; as, if we are to use gas economically, the flame must be the same shape as the vessel to be treated.

We may now consider the heating of blanks for stamping, hardening the points of spindles, finishing the ends of umbrella tips, and work where a small article, or a small part of any article, has to be heated to a high temperature with speed and certainty. For these a long and narrow flame is necessary, and I may mention that in cases where a high speed of delivery is required, and a small part only has to be heated, such as, for instance, in the hardening of the points of spindles for cotton machinery, I have made burners giving a flame of exceedingly high temperature only 1/4 inch wide and five feet long. This flame is produced by the assistance of a blast of air, and is of sufficiently high temperature to fuse the spindle in a few minutes.

The points only project over the flame, and the spindles are carried mechanically at such a speed that at the end of the five feet traverse they are red hot, and drop into water. More than one hundred are in the flame at once, lying side by side.

For heating blanks for stamping, the furnace bar-burner is perfectly suited, and in this work the chute supplying the blanks to the machine should be made of two fireclay sides, with an opening for the flame between the chute and flame being placed at a sharp angle, to prevent risk of the blanks sticking or overriding each other. A blowpipe may also be used with good effect, as shown in the above engraving, and in many cases it is preferable and much easier to manage.

In some cases the direct contact of the flame would spoil the articles to be heated, and instead of the arrangement mentioned, a tube of iron, fireclay, or other suitable material is heated, and the articles are passed through it. This system of continuous feed, through a tube, has been applied to the firing of small articles of pottery, and might possibly be well adapted, among other things, to the production of gas-burners.



Where the contact of air with the heated articles is injurious, many plans have been tried to keep the ends closed as much as possible, but I believe no more perfect and simple seal against the admission of air can be devised than to turn a jet of pure gas, unmixed with air, into each end of the tube. This is an absolute seal against the entry of oxygen in an uncombined state; free oxygen cannot exist at a very high temperature in the presence of coal gas.

For many trades there is a demand for hardened and tempered steel wire, either round or flattened, and the production of this has led to many attempts to obtain a satisfactory continuous process. The common method now, which is worked as a "secret" process by most firms, is to pass the wire through a tube to heat it, as already described, and to run it direct from the tube through a hole in the side of a box filled with oil, the whole being packed with asbestos, to prevent leakage; from this it is passed through another similar hole on the opposite side, either over a plate heated to the right temperature, or over a narrow open flame of sufficient length and power to give the correct heat for tempering.

Where absolute precision is necessary, the gas supply must be adapted by an automatic regulator on the main, to prevent the slightest variation of heat. Once adjusted, the production of flat and round spring wire by the mile is an exceedingly simple matter. It is quite possible to obtain absolute precision in temperature by a proper adjustment of the gas pressure, and as this is, for tempering steel articles and some other purposes, a matter of great importance, it is worth some consideration. No pressure regulator alone will give an absolutely steady supply; but if we put on first a regulator, adjusted to the minimum pressure of supply, say one inch of water, and then fix another on the same pipe, adjusted to a slightly lower pressure, say 9/10 of an inch, the first regulator does the rough adjustment, and the second one will then give an absolutely steady supply, provided always that the regulators are both capable of passing more gas than is likely to be ever required. No regulator can be relied on for absolute precision, if worked up to its maximum possible capacity.



Among other applications of a long narrow flame of high power, may be mentioned the brazing of long lengths of tube, in fact the application of flames of this form, with and without a blast of air, for different temperatures, are almost endless.

The thousands of uses to which blowpipes are adapted are so well known, that they need no mention, except the curiously ignored fact that the power of any blowpipe depends on the air pressure. A compact flame of high temperature cannot be obtained except with a heavy air pressure, and the ignorance of this fact has caused an immense number of unexplained failures. Many people think that one blower is as good as another, and expect that a fan giving a pressure equal to, say, the height of a two inch column of water should do the same work as a blower giving a pressure ten to twenty times as great. The construction and power of blowpipes, with the laws ruling the proportions and power, will be found in an article on "Blowpipe Construction," published in Design and Work, March, 1881, and as the matter is there fully treated, no further reference to the subject is necessary.

In the more recent forms of gas-engine, the charge is exploded by a wrought iron tube, heated to redness by the external application of a gas flame. This, although considered satisfactory by the makers, appears to me to be an exceedingly crude way of getting over the difficulty; and I offer it as a suggestion, that a very small platinum tube shall be used instead of iron. This, if made with a porous or spongy internal coating, would fire the charge with certainty, at a lower temperature than iron, and it could be made so thin and small in diameter, without risk of deterioration or loss of strength, that an exceedingly small flame could be used to heat it up. As it would be fully heated in a very few seconds, the delay in starting would be obviated.



There are many purposes for which a red heat is needed for slow continuous processes on a small scale, such as case-hardening small steel goods, annealing, heating light steel articles for hardening, and a great variety of other similar processes. This, until recently, has required the use either of a rather complicated furnace, or a blast of air under pressure, to increase the rapidity of combustion. Since the conclusion of my experiments on the theoretical construction of burners, I have found that the high-power burners, previously described, are capable of heating a crucible equal in size to their own diameter to bright redness without the assistance of a chimney, provided the crucible is protected from draughts by a fireclay cylinder.

This is an important point, as it renders the production of a continuous bright red heat a matter of the greatest ease, even in crucibles of a comparatively large size. Where the heat is steady, and certain not to rise above a definite point, it can safely be used for such purposes as hardening penknife blades and other articles which are very irregular in thickness, the thin edges not being liable to be burnt or damaged by overheating.

For the highest temperatures air under pressure is a necessity, as we require a large quantity of gas burnt in as small a space as possible with the maximum speed, and given this air supply, we are very little hampered by conditions, as an explosive mixture may be blown through a gauze into a fireclay chamber, closed, except so far as is necessary to allow the escape or burnt gases. The speed of combustion is limited only by the speed of supply of air and gas, and by increasing these there is no practical limit to the heat which can be obtained. When we have to do with the reduction of samples of refractory ores, testing the comparative fusibility of different samples of firebricks, or alloys, etc., the use of an explosive mixture blown into and burning in a close chamber is invaluable, and the ease and certainty with which any temperature may be obtained has led to great discoveries, and the revolutionizing of many commercial processes. Recent experiments have proved that, by a modification in the form of the well-known injector furnace, an enormous increase of temperature may be obtained. I have, in actual work, obtained the fusing point of cast iron in two minutes, starting all cold, and have fused every furnace casing I have yet been able to produce. If infusible casings can be made, I think I am not overstating facts in saying that any temperature required can and will eventually be obtained with the greatest ease. What the limit is I have as yet not been able to discover.

There is one more application of gas, as a fuel, which, discovered and published by myself some two years ago, has yet to become generally known, and in some special processes may prove exceedingly valuable. This is the addition of a very small quantity or coal gas, or light petroleum vapors, to the air supplied by a blower or chimney pull, to furnaces burning coke or charcoal. The instant and great rise in temperature of the furnace, and the greater stability of the solid fuel used, are extraordinary. This is, in fact, a practical application of the well-known "flameless combustion," the only signs that the gas is being burnt being a great rise in temperature and a decreased consumption of the solid fuel; in fact, if the gas is in correct proportion, the solid fuel remains unburnt, or nearly so, in spite of the high temperature. In cases where a sudden rise in temperature is required in a furnace, or where the power is deficient, this method of supplementing and increasing the heat will be found of very great service, and processes liable to be checked by making up a fire with fresh fuel can be carried on without check, even after the solid fuel has almost entirely disappeared.

That a solid fuel is quite unnecessary, I will prove in a very simple manner, by burning a mixture of coal gas and air without a flame, in a bundle of iron wire. The heat is sufficient to fuse the wrought iron with ease, and the glare inside the bundle of wire is painful to the eyes. The same result could be obtained by a pile of red-hot lumps of firebrick, and the same heat obtained also without a trace of flame.

It is not possible to enter fully into such a wide and important subject in a single lecture, and the suggestions now given are simply hints for the guidance for those who need or desire to experiment. No doubt we shall have, after a time, some text-books and other literature on this subject, which is one of great importance to many industries; and it is necessary for experimental work and applications to new industries, that the experimenter shall not only be able to purchase special burners, but that he shall have fundamental laws laid down which will enable him to construct them for himself, so as to have his experiments under his own control. The difficulty in the way of literature on the subject is that those few who have worked in the matter are busy men, with little time which is not already fully employed.

Pioneers on new ground have a great liability to generalize and jump at conclusions, and the necessary exact work and detail must, to a great extent, be left to those who follow on tracks already roughly marked out.

Of the special trades which have come under my observation, I have only had time to mention a very few. It appears to me that there are very few manufacturing processes of any kind which could not be simplified by the use of gas as a fuel, from the production of electric light apparatus to the manufacture of explosives, cotton stockings, beer, catgut, glue, umbrellas, ink, fish-hook, medals, stained glass windows, brushes, and other trades equally various, which come daily under my own notice.

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A man was received into the Laborisiere Hospital, Paris, the other day, with a yard of rope hanging from his mouth. Traction upon the cord revealed a section of clothes line measuring eight feet. He had been surprised in an attempt at suicide and had tried to conceal his design by swallowing the cord. He lived, of course—they generally do.

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INSTANTANEOUS PHOTOGRAPHY.

A certain number of the readers of this journal are occupied with photography, and all assuredly are interested in this marvelous art, whose progress is so remarkable. So it has seemed to us that it would be of interest to treat of a question that is the order of the day. We desire to speak of those photographic apparatus called instantaneous shutters.

Numerous apparatus of this kind have been proposed to the public, and several even have been described in this journal, but we have to state that, despite the success in certain cases, none of them has proved remarkable for its qualities and superiority. This is due, we believe, to the fact that inventors, while showing arrangements that were often ingenious, have not always taken into account the end that the shutter is to subserve, and the qualities that it must possess in order to attain such end.

In face of the progress made by extra rapid dry processes, the question of shutters has become the most important, since cabinet-making, optics, and photographic chemistry give us apparatus, objectives, and products which, although they will doubtless be improved upon, satisfy for the present all our needs.

What is understood by instantaneousness? To our knowledge, no definition thereof has as yet been given. For our part, we propose to style "instantaneous" any photograph that is taken in a fraction of a second that our senses will not permit us to estimate. The shutter is the apparatus which allows the light to enter the photographic chamber during this very short time.

In order to examine the different rules that govern the question of shutters, we shall take as an example the type styled the "Guillotine."

This apparatus, as every one knows, is a stiff plate containing an aperture and passing over the line of the rays of light. Some place it in front and others behind, while others again place it within the objective. Let us examine and discuss what occurs in the three cases. Suppose a rectilinear objective of the kind most usually employed in instantaneous photography, and an object, A B, that we wish to reproduce (Fig. 1), the objective being provided with any sort of diaphragm. The point, A, sends a bundle of rays, a"b", to the first lens. Here they are slightly refracted, and then go on parallel lines to the second lens, where they are again refracted and form at A' an image of A. It is this image that we see upon the ground glass, and which makes an impression upon the sensitive film. The point, B, behaves in the same way and gives an image at B', but, as will be at once seen, the image will be reversed. In our figure, A corresponds to the sky and B to the earth. If, then, the shutter passes in front of the objective, it will first allow of the passage of the rays which come from the sky, then, on continuing its travel, it will unveil the landscape, and lastly the ground. As it is submitted to the law of the fall of bodies and has a uniformly increasing velocity, it follows that the time of exposure will uniformly decrease between A' and B', and that the sky will pose longer than the foreground. Such a result is contrary to all photographic rules, which require that objects shall pose so much the longer the less they are lighted. This position of the "guillotine" shutter is absolutely false, and must be altogether discarded. If the shutter be placed behind the objective, it will follow, as a consequence of the same demonstration, that the time of exposure will go diminishing from B' to A', and that the foreground will be exposed longer than the sky. The solution is logical, then, and will permit of obtaining excellent negatives.



Let us now examine how the image, A'B', is formed. The point, A, appears first, and becomes lighter and lighter up to the moment at which all the rays that emanate from the point, A, are unveiled. The point, B', is not yet visible. As the shutter continues its travel the point, B', appears in its turn and becomes illuminated like the point, A'. At this moment the objective is completely uncovered; the image, A'B', is perfect, and possesses its maximum intensity. Then the point, A', gradually becomes obscured and disappears; and the same is the case with all parts of A'B'. The image is developed progressively from A' to B', and makes its impression upon the sensitive plate successively—a fact which, as may be conceived, may have its importance. If, for example, we are photographing a ship that is being tossed about by the sea (and we borrow this example from our colleague, Mr. Davanne), the image of the top of the mast will not be formed at the same instant as that of the base, and if the motion of the mast has sufficient extent it may take on a curved form, due to the fact that it has effected a movement between the moments during which its apex and base were being photographed.

Upon placing the guillotine shutter in the optical center of the objective, what will occur? The shutter will permit the passage of an equal fraction of the rays derived from A and B, that is to say, the image will be complete from the first instant of the exposure. The points, A' and B', will be illuminated precisely at the same moment. As the shutter continues its travel, a fresh quantity of rays coming from A and B will be admitted, and the image will be illuminated more and more up to the moment at which all the rays can pass. It will then possess its maximum intensity. Then a portion of the rays from A and B being intercepted, the image will become darker and darker until complete extinction. The image here, then, is not produced successively as in the former case, but is entire from the beginning. In this case the image of our mast cannot be misshapen, since it has been accurately photographed at the same moment.

The true place for the guillotine shutter, then, from a theoretical standpoint, is in the interior of the objective. Are there any other advantages to be gained by so placing it? Yes; it is easy to understand that for the same time of exposure, and consequently for the same result, the aperture may be so much the smaller in proportion as the optical center is approached.

The luminous rays, in fact, form in the objective a double truncated cone whose upper base is equal to the diaphragm, and the lower one to the diameter of the lenses. If the aperture be equal to any diameter whatever of one of the cones, the result will be the same; but, for the same period of exposure, it will evidently prove advantageous to approach the diaphragm. The ratio of the apertures that give the same results at the optical center or behind the objective is as that of the diaphragm employed to that of the back lens. If the diaphragm is one centimeter and the lenses four centimeters, an aperture of one centimeter in one case and of four in the other will give the same result.

We shall see further along that it is advantageous to employ apertures equal to several times the diameter of the diaphragm or lens. Now, from what we have just said, an aperture, equal for example to four times the diaphragm, will be only 4 centimeters, while the corresponding aperture behind the lens must be 16. The dimensions of the first will be practical, and those of the second will give too cumbersome and too fragile an apparatus. But why must the aperture be larger than the diaphragm employed? This is what we are going to demonstrate. Let us make the aperture equal to the diameter of the objective, and see what occurs at the different periods of the exposure. For the sake of clearness, we shall suppose the velocity uniform.