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The valve at the end of the rod, attached to the lever, L, being kept shut by the catch, M, the screw plug, H, removed, the acid is introduced through the aperture thus opened. In the next place, the plug being replaced, and the valve depressed by means of the lever and rod, so as no longer to close the opening, which it had occupied, the acid descends from the chamber into the cavity of the vessel beneath it. The valve is of course restored to its previous position as soon as the acid has effected its descent.

The lowermost vessel is furnished with a perforated copper tray, supported by a copper sliding rod, in a way quite analogous to that already described in the case of the copper reservoir. It is also supplied with zinc and its solvent in like manner, being made half full of the diluted sulphuric acid. Of course, on contact being produced between the zinc and its solvent, the generation of hydrogen will take place. So long as the communication between the upper portions of the two vessels is open, the gas will extend itself into both, occupying the whole of the upper vessel, and that half of the lower one which is unoccupied by the liquid, But if, in this way, the pressure reaches to two atmospheres, as indicated by the gauge, * on shutting the communication through the pipe, B, the pressure in the inferior vessel will augment, that in the superior vessel remaining as before, but the liquid will consequently begin to pass out of the inferior vessel through the pipe A, and thus may lessen the contact between the acid and zinc, and finally suspend it altogether. Meanwhile the gas in the upper vessel being condensed to nearly half its previous hulk, the pressure will be nearly four atmospheres. It will, in fact, always be nearly double that which existed before the pipe, B, was closed.

In order that nearly the whole of the acid shall be expelled from the inferior vessel, the tray must be depressed till it touches the bottom of that vessel.

The pressure being four atmospheres at commencement, as soon as, by means of a pipe attached to the valve-cock, N, an escape of gas is allowed, the acid is forced again upon the zinc, and thus prevents a decline of pressure to any extent sufficient to interfere with the process.

The gases may be used from a receiver in which they exist, in due proportion, safely by the following means :

Two safety tubes are to be made, not by Hemming's process exactly, but as follows:

A copper tube, silver soldered, of which the metal is about the eighth of an inch in thickness, is stuffed with the finest copper wire, great care being taken to have the filaments straight and

I have used for a gauge an instrument like G, fig. 5, the lube being about two feet in length, and sealed at the upper end.

parallel. The tube is then to be subjected to the wire-drawing apparatus, so as to compress the tube on its contents until the draught becomes so hard, as that it cannot be pushed farther without annealing. The stuffed tube thus made is to be cut into segments, in lengths about equal to the diameter, by a fine saw. The surfaces of the sections are to be filed gently with a smooth file. By these means, they appear to the naked eye like the superficies of a solid metallic cylinder. Brass caps being fitted on these sections, they are to be interposed by soldering, at the distance of a foot or more, into the pipe for supplying the jet. Under these circumstances, the posterior section becoming hot, may allow the flame to retrocede; but the anterior section being beyond the reach of any possible combustion, and remaining cold, will not allow of the retrocession; and as soon as the flame passes the first section, the operator, being warned, will, of course, close the cock, and subject the posterior section to refrigeration before proceeding again.

But this plan of operating may be rendered still more secure by interposing a mercury bottle, or other suitable iron vessel, half full of oil of turpentine, between the reservoir and safety tubes, as in the arrangement of a Woulfe's bottle. A leaden pipe proceeding from the reservoir is, by a gallows screw, attached to an iron tube which descends into the bottle, so as that its orifice may be near the bottom. The leaden pipe communicating through the safety tubes with the jet-pipe, is attached to the neck of the bottle. Thus the gaseous mixture has to bubble through the oil of turpentine in order to proceed through the safety tubes to the jet-pipe. If, while this process is going on, the flame should, by retrocession, reach the cavity of the bottle, exploding in contact with the turpentine, a compound is formed, which is, per se, inexplosive from the excess of carbonaceous matter. Meanwhile the shock, acting on the surface of the oil, drives it into the bore of the iron tube, and thus, both by its chemical and mechanical influence, renders it utterly impossible that the flame should reach the cavity of the reservoir.

Apparatus for the Fusion of Iridium or Rhodium or masses of

Platinum less than five ounces in weight. For the fusion of either Iridium or Rhodium or masses of Platinum not exceeding the weight of half an ounce, an instrument with three jets has been employed, the bore of each jet pipe being such as not to admit a wire larger than the 's of an inch in diameter. The flame produced by these means was quite sufficient to envelope the mass to which it was applied.

In fusing any lumps or congeries of platinum, not exceeding five ounces, an instrument has been used capable of giving seven jets of gas, issuing of course, from as many pipes. Of these pipes, six protrude through the brass casting forming the bottom of the copper case constituting the refrigerator, so as to be equidistant from each other upon a circumference of three-fourths of an inch in diameter, the seventh protruding from the centre. The bores of these jets are such as not to admit a wire larger than g'a of an inch in thickness. Those of the larger instruments represented by the accompanying engravings were such as to admit wires of zöth of an inch in thickness.

The jet-pipes may be made by the following process :—A thin strip of sheet metal, somewhat wider than the length of the circumference required in the proposed pipe, after being roughly turned about a wire so as to form an imperfect tube, is drawn through several suitable holes in a steel plate, as in the wiredrawer's process. Under this treatment the strip becomes converted into a hollow wire; the edges of the strip being brought into contact reciprocally, so as to leave only an almost imperceptible crevice. Having drawn one strip of platina in this way, another strip sufficiently wide nearly to enclose it, is to be drawn over that first drawn, care being taken to have the crevices left at the meeting of the edges on contrary sides. The compound hollow wire or tube thus fabricated, is finally to be drawn upon a steel wire of the diameter of the requisite bore.

The following method of making jet-pipes, though more difficult, is preferable; as there is less liability of the water of the refrigerator leaking into the bore.

Select a very sound and malleable cylinder of platina, of about three-eighths of an inch in thickness, perforate it by drilling in a lathe, so that the perforation may be concentric with the axis. A drill between th and th of an inch in diameter may be employed. In the next place the cylinder may be elongated by the wire-drawing process, until the proper reduction of metallic thickness is effected, the diameter of the bore being prevented from undergoing an undue diminution, by the timely introduction of a steel wire.

Of course, the metal must be annealed as often as it hardens, by drawing. For this purpose, a much higher temperature is necessary in the case of platinum, than in that of either copper, silver, or gold.

The annealing is best performed by the hydro-oxygen flame. If charcoal be used, the greatest care must be taken to have the fireplace clean.

Agreeably to a trial made last spring, palladium may be used as a solder for platinum ; and as it is nearly as difficult to fuse as this metal, it is of course, for that purpose, preferable to gold where great heat is to be resisted. No doubt, by employing palladium to solder the exterior juncture of the double drawn tubes above mentioned, they might answer as well nearly as when constructed of solid platinum.

ART. VII.Description of Two New Species of Fossil Foot

marks found in Massachusetts and Connecticut, or, of the Animals that made them; by Rev. EDWARD HITCHCOCK, President of Amherst College, and Professor of Natural Theology and Geology.

I have long wished to describe several new and peculiar fossił footmarks which have been brought to light in the sandstone of the Connecticut Valley in Massachusetts and Connecticut. But a constant pressure of more important duties has delayed the work, not months merely, but years. I have determined, however, to begin it; hoping that time and health may allow me to prosecute the descriptions in future numbers of the American Journal of Science. For the present I content myself with describing two species ; one of them, if I rightly understand it, of most extraordinary dimensions and character.

Before the Association of American Geologists and Naturalists, at their meeting in New Haven, in 1845, I communicated a paper, in which, instead of naming the tracks, as I had formerly done, I attempted to name the animals that made them. That paper I have never found time to get ready for the press; though a list of names was given in the Proceedings of that Society. I am more and more satisfied that this principle, suggested to me by my friend, Mr. James D. Dana, is the true one by which these singular relics should be described.

I have been surprised, however, to learn that some object to giving scientific names, either to these footmarks, or to the animals that impressed them; because they think the characters by which they must be described too indefinite for distinguishing species, or even genera. My reasons for a contrary opinion are briefly as follows.

1. The existence of these tracks demonstrates the existence of certain animals that made them during the triassic period. 2. The facts well known concerning organic remains, render it almost certain, that these animals have never been described, either in the living or fossil fauna of any country. 3. All who have seen a good collection of these tracks, will be satisfied that they were made by several species of animals. Now this conviction must result from some diversity of character, which we witness in these footmarks. And if that diversity could produce such a conviction, it can be expressed in words; and thus the different species, at least many of them, be distinguished from one another. If they cannot thus be distinguished, then they must be regarded as only varieties of the same species. But no comparative anatomist will admit this to be possible. 4. Comparative anatomy teaches us that some of the surest and most constant characters by which animals are distinguished, are derived

from their feet. This is eminently true of birds. “Indeed," says Duméril, “it is by the form and the length of the feet, and the disposition of the toes, that birds are divided into six orders, &c.* 5. Living animals could to a great extent be divided correctly into families, genera, and species, by their tracks. 6. If no fossil animal is to be named until we obtain a complete description of it, then a large part of those already named, should be stricken from the list of organic remains, since only fragments of their skeletons have been found; and we have the authority of Cuvier for saying, that sometimes even the whole skeleton is insufficient to distinguish species from species. “ The difference," he remarks," between two species is sometimes entirely inappreciable from the skeleton. Even the genera cannot always be distinguished by osteological characters.”+ My conviction is, that not a few fossil animals have been described from characters much more uncertain than those derived from well preserved tracks. 7. We have the highest authority for naming animals from their tracks alone. This was done by Professor Kaup, in the case of the Chirotherium; and by Professor Owen, in the case of the Festudo Duncani ; the only evidence of whose existence is the tracks on the sandstone of Scotland. I 8. Convenience in writing or conversing about different kinds of these relics, demands that scientific names should be attached, either to the tracks or the animals that made them. In making attempts to describe them without names, I have sometimes been reminded of the house that Jack built, in an old nursery story: Ex gr., " this is the dog that worried the cat, that killed the rat, that ate the malt, that lay in the house that Jack built.”

Upon the whole, I cannot see why it is not as desirable, and as consonant to the laws of zoology and comparative anatomy, to derive the name of an extinct animal from its tracks, as from a fragment of a skeleton. Admit that in most cases there may be more danger of mistake in the former than in the latter instance : yet in the first case there is almost every possible degree of uncertainty as to the exact place which the animal ought to occupy. But if well assured of its former existence, why should it not have a name assigned it, among the preadamite inhabitants of the earth, according to the rules of nomenclature derived from zoology and comparative anatomy? So far as these sciences will justify distinctions, and no farther, do I contend for the erection of genera and species. In the present instance, I have so constructed the generic and specific names that they will hold good, though future researches should prove the animals to have been very

different in nature from what we now suppose. Fur

• Elemens des Sciences Naturelles, Tome ii, p. 258, fourth edition.
* Ossemens Fossiles, Tome troisième, p. 524, third edition.
* Rep. of Brit. Assoc. for Advancement of Science, for 1841, p. 160.

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