long flue leading under the eight pans or steamers placed side by side. Figures 2 and 2a represent a pair of banks in plan. Figure 2 is a horizontal section. Figure 2a represents the bank in a complete state, as seen from above. Figure 3 presents an elevation or external view of the front of the furnace, and also a section through pan or steamer No. 1, in the plane B B. It shows the interior of the fire place and ash pit. Figure 4 presents an external view of the back end of the furnace bank, with cross section of the flues, and a section in the plane C C, or through pan or steamer No. 9. Figure 5 is a vertical cross section at the middle of No. 3 steamer, with a further part of the bank, shown in oblique projection, in perspective view, with the point of distance very far removed, in order to show the form of one of the hand syphons and its position when in use.

REMARKS UPON THE FURNACES.

The furnace is very simple, but is adapted to economize fuel, and to consume smoke to a great extent when properly stoked. The surface of the fire-grate is made large enough to burn "brise," (sifted cinders,) or other poor kinds of fuel, while doing full work.

A flap of sheet iron should be hung against and cover the upper part of the entrance of the ash-pit, and be so adjusted as to cause a considerable proportion of the air to be drawn through the chinks which ought to be left in and around the door of the furnace. It is preferable to have the ash-pit closed from above, as described, than at the sides.

The bottoms of steamers, which are five feet by six feet, are not level, but slope two inches in the forty-eight and one-third feet toward the furnace; they also slope two inches in the six feet toward the outer sides of the pair of banks. Their sides are also inclined outwards three inches each from the perpendicular on the sides of the bank, and one and three-eighths inch on the sides next to the adjacent steamer.

The iron plates on which the steamers rest should be made of a single piece, one being placed under each steamer. The lower sides of these iron plates rest on small cast-iron wall plates leading to a small gutter, so arranged as to carry off the acid escaping by leakage, which would otherwise be lost, and by entering into the brick work gradually destroy it.

COVERS OF STEAMERS.

The covering boards are one inch in thickness, coated with the thinnest sheet lead, (two pounds per square foot.) They are supported at each end of the steamer by a frame resting on the brick work, and made of bar iron one inch square, likewise coated with lead. A sheet of thin lead hangs from these iron frames, to prevent draughts of air across the steamer. A narrow space is left between the edges of the lowest covering boards and the upper edges of the sides of the steamer, to allow a current of air to enter, which makes its exit at the top of the

cover, where, between the two edges of the cover, a wider space is left, sufficient for ventilation and for carrying off the watery vapor, but not so large as to allow the acid to become cooled by more air passing over it than will remove the vapor, or the heat to escape by radiation, as is the case to a very large extent when the steamers are left without

covers.

The apparatus here described has been long in use, and has been found to be both economical, durable, and convenient. Bars instead of plates are used quite often under the coolest steamers. An economy of fuel is undoubtedly effected by this arrangement, not merely by the lead being exposed directly to the action of the heat, but also by the gases as they glide past being retained by the projecting bars. Steamers, however, supported in this way, are more liable to injury from careless treatment, and the arrangement is not to be recommended.

The pair of banks, such as represented, when in moderate work, can concentrate sulphuric acid from 115° Tw., or 1.575 sp. gr., to 154° Tw., or 1.770 sp. gr. It is then ready for rectifying in the platinum vessel, which gives 10,000 pounds of vitriol each twenty-four hours.

PLATE VII.

PLATINUM STILL, HAND SYPHON, AND STEAM JET.

PLATINUM STILL.

The still here represented is from the establishment of Johnson Matthey & Co., manufacturers of platinum, Hatton Garden, London. Two or more were exhibited in the case containing the platinum apparatus sent by this firm to the Exposition.

The body of the still is twenty-eight and one-half inches broad at the base and thirty-six inches at the widest part above. The total height from the bottom to the top of the hood is thirty-eight inches.

HAND SYPHONS.

These are of platinum, and one is shown in section sideways and as it appears from behind. The dimensions are given upon the plate. The figures are about one-fourth of the actual size.

These syphons are capable of being filled or emptied without the usual trouble, and of being carried about without losing their charge. They are more simple than a cupped syphon, and draw from the bottom of the steamer. They deliver freely, and while in use in liquors evolving gases (the steamers sometimes evolve sulphurous and nitrous gas) these syphons, each having an air chamber, retain their charge a much longer time than an ordinary syphon can under similar conditions.

For connecting steamers in the hotter part of the bank, the syphons

need not be made with the air chamber, unless the acid is frequently of very bad quality, containing much gas. The smallest depth of liquor in which this syphon can be charged is six and one-half inches.

STEAM JET FOR CHAMBERS.

Steam jets are made of chemical stone-ware. Those manufactured by the Messrs. Cliff, at the Imperial Potteries, Lambeth, London, are porous, baked at a heat below vitrification, and are not glazed. These withstand the effect of acid gases and the sudden heat of steam, and will maintain a uniform jet of high-pressure steam, which can be regu lated by chipping off the indented end of the jet. This jet-hole does not clog or enlarge as with a leaden jet. The conical exterior insures a close fit into a smooth circular hole in the sheet lead forming the top of the chamber, and without enlarging the hole by wedging too tightly into it.

APPENDIX.

COLORING MATTERS DERIVED FROM COAL TAR.

EXTRACT FROM THE REPORT OF DR. A. W. HOFMANN.

"This is no longer an age in which an industry requires many years for its creation, and still longer time for its development and expansion. "Jealously guarding the processes employed, hiding with care the raw materials used, a manufacturing process formerly was hid in an obscurity which had the effect of confining a profitable monopoly to the country where it was first established. The privileges conceded by the rulers, a host of legislative enactments, general ignorance, and the special organization of labor, all tended, at a period anterior to 1789, to favor this result.

"In our days, a useful discovery is scarcely made, or a happy application of one found out, before it is published, described in the scientific journals or other technical periodicals, and especially in the specifications of patents. It then becomes the starting-point of a thousand researches and new experiments, entered into by the philosopher in the hope of advancing scientific progress, and by the manufacturer with the expectation of reaping a material benefit. From these multiplied and diverse efforts, these incessant labors of an army of workers, arises an industry which has no sooner sprung into existence than it becomes important and prosperous. Moreover, it is not only in the land of its birth where its development takes place; it extends rapidly in foreign countries, so that it not unfrequently happens that the place where the discovery has originated is distanced in the applications of it by neighboring states. The ocean itself is no longer a barrier between the nations which it separates. New York, in an industrial sense, is now a neighbor of London, Paris, and the German centers of industry.

"The history of the artificial coloring matters derived from coal abounds in illustrations of this. It only dates from the end of 1856, and yet what success it had achieved in the Exhibition of 1862!

"From that date, owing to the number, variety, beauty, and value of its products, and from the large scale on which it was carried on, it might rank with the largest industries. In 1862 the value of these manufactures had risen from nothing to ten millions of francs; at the present day this sum is trebled, and still the products are much cheaper

than they were before. Indeed, the improvements successively introduced into the manufacture of the tinctorial products derived from coal have had the result not only of rendering them more beautiful, but at the same time of reducing their cost in such a manner that aniline colors can successfully compete in price with any other coloring matter of equal tinctorial power; so that if they were formerly purchased on account of the unexampled brilliancy of their tints, they will retain their importance owing to the low price at which they can be produced.

"Among the coloring matters which were already known in 1862, some have now become true raw materials, from which are produced other coloring matters equally beautiful, equally rich, and of no less importance than those from which they have sprung.

"Thus, rosaniline has become the parent of a whole series of colors, and last of all of a green. The gamut of coloring matters derived from aniline is now complete; we have red, orange, yellow, green, blue, indigo, and violet.

"Are we not justified in saying that the manufacture of artificial coloring matters, in spite of the improvements of which it is yet capable, in spite of the discoveries which will yet enrich it, and scarcely ten years old, has emerged from the state of infancy, and become one of the most important industries of the age?

"But if the development of this new branch of manufacture has attained so high a point in so limited a time, its publication and diffusion through the industrial and commercial world have advanced with still greater rapidity. The first of the aniline dyes in order of date is mauveine. This was discovered in the month of August, 1856, by Mr. W. H. Perkin. Whilst the inventor, young, and of ample resources, remained for nearly two whole years before he could carry out his invention on a large scale, and strove against the difficulties which beset the introduction of all new discoveries, several French manufacturers produced mauveine immediately, and on a large scale, by the actual process (or but slightly modified) which was revealed to them by the English patent. One who only considered the state of the industry at this time in the two countries, would have said that the invention belonged to France, and had only been imported into England. From France it almost at once spread to Germany.

"In 1859 aniline red was produced. Scarcely three months after its production was commenced at Lyons it was transplanted to Mulhouse; then crossing the Channel, it became established in England, at London, Coventry, and Glasgow, and was not long before it was taken up in Germany.

"Aniline blue first appeared in 1860. Less than a year afterwards it took ten manufactories in Germany, England, Italy, and Switzerland to produce this new material.

"While the manufacture of aniline colors thus became European, their consumption spread still further; and now could be observed this