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at the place where a sharp edged collar is plaeed to prevent a soft metal band from being forced out of the gun in advance of the shot. The soft metal band will take the grooves and give the shot the rifled motion, but will not hinder the shot in its passage through iron plating, against whieh it is projected. When used as a shell, it is intended to ignite the powder it contains by the heat of compression resulting from the blow against the plating. The small inclined and inclosed tube is intended to contain common powder, and it is inclined toward the front of the shell that the compression may not entirely close the passage to the powder contained in the cavity of the shell, but rather only close its front end first.

GREAT CAST IRON GUNS.

The last gun I shall describe, exhibits the result of my efforts to produce a cheap.gun of larger size than has been before produced, constructed, how

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ever, with full knowledge of all the effects of combustion of the powder by pressure, as laid down by ordnance officers in books heretofore, and the

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effect of leat discovered by myself. In this gun I provide strength to resist the pressure of the powder, while I compensate for the effects of heat, by superior elasticity, not only for the unequal expansion in the direction of the diameter, but of length also. The gun is to be cast so near to the required dimensions as to need no turning outside, thus preserving the most enduring surface to the casting, and allowing it to compensate by increased elasticity effectively for unequal heat in its inner and outer portions when made of one metal, as homogeneous cast iron.

The figures are a longitudinal section and a cross section of a gun constructed according to this invention. The passages are cast with cores to leave webs in the doubly curved form represented. The cores between the webs, as also a core forming the bore, may be cooled by tubes containing

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water or other cooling agent, in the manner patented by Captain Rodman, if preferred. When the gun is fired, the heat communicated to the interior surface expands the central portions of the casting. The open

condition of the iron intermediate between at

the inner, portion b and the exterior portion 61 of the thick part or re-enforce of the gun, allows this portion of the structure to yield

by its elasticity, both laterally and longitudinally, far more than when the gun is cast solid; so that the strain, whether purely mechanical, i. e., due to the expansive force of gases, or due to the heat of the interior, or, as will generally be the case, due partly to both, is allowed for, first, the pressure by the strength of the re-enforce; second, the expansion due to heat, by the elasticity of the webs. The re-enforce being cast of a somewhat greater thickness than other parts of the gun, will cool last, and shrink to the required pressure against the webs, and through them upon the inner metal. I can furnish these guns for five cents per pound, there being no machine labor necessary upon them except drilling the vent. I propose to cast the bore.so near the proper size as not to require boring, and thus leave about the bore the most enduring surface. The gun, too, being cooled from so much surface, will be of a more uniform structure than has been before attained.

I am a manufacturer, and whatever facility of adaptation I may exhibit, is directly devoted to arranging plans for the purpose of making proposals for the manufacture of the work designed in a practical manner, with a view to that end only. My designs are the result of long study and close application, assisted by a long practical experience in constructing machinery and working metals. Whenever exhibited, these plans have received a hearty approval from practical men,

I have specified three general plans for the fabrication of large guns, adapted to the various requirements of service. The spherical gun and turret will answer as well for an iron-clad ship as a ram, although the weight of the gun and the thickness of the turret are greater than those heretofore proposed; the smaller diameter of the turret enables me to construct it to have no greater whole weight than the Ericsson turret with its guns; and when so constructed, it is a smaller object to be aimed at

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by hostile guns. The lightest of its projectiles, the one with the hollow rear, weighs 780 lbs. When this shot is used, the cubical contents of the bore and the hollow base of the shot are about six times the cubical capacity of 60 lbs. of fine powder, and that charge would thus be well utilized, giving a respectable velocity to the greater weight of projectile than has ever before been thrown. No ship can be made to carry plating that will resist it, except its size is so great that it cannot enter any of our harbors.

These guns, adapted to such tremendous projectiles, can then be mounted in turrets of such thickness of iron as to resist projectiles from any other gun now made, or likely to be made, if the turret rests on a solid foundation, as in the fort proposed for harbors; and will afford' absolute protection to them without involving extravagant cost of either money or material. The accelerating gun described is available for fast wooden or iron steamships, and, from the extraordinary velocity they impart to the projectile, will penetrate iron-clad ships at very long ranges

The cheap cast iron gun completes the list, and is available for other requirements of service, for which large calibers are desirable, and as the principles involved in my statements only affect large guns, I shall discuss the subject of small guns at another meeting. Adjourned.

Thomas D. STETSON, Secretary.

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AMERICAN INSTITUTE POLYTECHNIC AsssociatION,

December 26, 1862. The Chairman, S. D. Tillman, Esq., presiding.

Mr. J. H. Churchill alluded to the difference of gases, and thought the fact that two gases in separate chambers would each expand into the other without change of heat, proved the truth of the dynamical theory of heat.

Prof. Seely, Mr. Dibben and Mr. Bartlett differed from him, and thought the action was a mere mixture and not properly an expansion of either gas.

Mr. J. K. Fisher doubted the theory that the gases would intermingle so rapidly as each gas would flow into a vacuum.

The Chairman read from the Transactions of 1857, the report of his remarks made on June 10, of that year, on the practicability of a telegraph to Europe by way of Behring's strait. He added that news has now arrived that the Siberian portion of the line is now being rapidly progressed with; a line has been nearly completed from St. Petersburg eastward to the Amoor river, while our own lines have been extended to the Pacific.

The regular subject, “Improvements in Modern Warfare,” was then

taken up.

The Secretary explained some of the recent improvements in fuses which have been lately invented and introduced with success for rifles, cannon and shells.

He described and explained particularly Schenkl's fuse, already largely introduced into the service,

Mr. J. K. Fisher said that it is shown by recent reports, that the Whitworth shells, before alluded to, did penetrate and explode behind 51 inch iron plates. They were exploded by the heat of compression of the iron in striking...

Mr. J. H. Churchill doubted whether the beat of compression was the cause of firing.

Nr. F. Dibben alluded to the facts and theory with regard to large guns, brought forward by Mr. Wiard at a previous meeting. The heat he (Mr. D.) thought could not expand the inside so as to very greatly affect the strength of the gun. In the old way of testing guns by firing many times with extra charges, more than half those failed on the first fire. He had seen it in six different cases of trials at Kingston, N. Y. Iron is stronger as it is heated up to 200° or 300° F. Experiments had as yet failed to show how far the heating beyond these degrees would improve the strength, but it had been determined that elasticity was of more value than actual tensile strength in cast iron. Greenwood iron would spring very sensibly.

Mr. Wiard remarked that wrought iron would bend still further.

Mr. Dibben confessed that elasticity was not the only quality required. Hardness and stiffness were also necessary. Mr. D. referred to the shortness of the bore of Mr. Wiard's design for a spherical gun of three different metals, and thought a longer bore, with slow-burning powder, would serve more efficiently to project the ball. Mr. Wiard proposed to make his bore only about five calibers long. The old plan for small arms was to make them sometimes thirty calibers long. This was now shortened with good effect, but he thought five calibers were too short.

Mr. Wiard explained that'he rated his guns to the length of cartridge. He thought that about five times the length of cartridge was a good proportion for nearly all arms, to get the best possible projectile force from the powder.

Mr. Dibben thought the heat produced by the burning of gunpowder in a space absolutely confined, was about ten thousand degrees Fah., and presented several grounds for the opinion. Powder in firing and cooling down the gases, occupies a space about 270 times that occupied when in a solid state. If the cooled gas was again compressed suddenly in a non-conducting vessel to its original volume, its heat,' by the known laws of heat due to compression; would be about that above given, i. e., 10,000° Fah.

Guns were often 'weakened by unequal cooling, due to the construction of the flask in which they were cast. He had cast a number which on extreme test burst along the lines of the junctions of the flasks. Guns could be cast without trünnions in a one part flask. The heat of the interior, as at first stated, was not sufficient to burst or greatly weaken the gun.

Mr. Bartlett explained the theory of Mr. Wiard and Mr. Reid, in ascribing the rupture of guns in part at least to heat. )

Mr. Wiard confirmed the estimate presented by Mr. Dibben, of the temperature of the gases of powder, but differed from him in believing that it had a very serious effect on the gun in expanding its interior. The temperature of 10,000 or more, exactly 10,800° F., was many times that of melted iron, and he had believed; 'until recently, that he was the first to show that it had or might have very great influence in bursting guns, Slow powder acts more equally on a gun, by reason of not fully burning TAM. Insr. 7

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until the shot is near the muzzle. Quick burning makes no more heat or power, pound for pound, but applies it to more advantage by acting with greater force at the beginning, and the same near the muzzle, as slow powder, if the guns will bear the strain. He (Mr. W.) proposed guns that should endure this strain and consequently would allow of the advantageous use of quick powder, Mr. Dibben explained on the blackboard that the muzzles of guns

received more heat than the breech, and therefore the metal at that part should become hot before the latter from another cause than its reduced thickness. He thought, on motion of the gases at their release, by presenting fresh particles of the heated gas to the surfaces, more rapidly than at the breech, where it was relatively stagnant, allowed the metal to receive, near the muzzle, more actual increments of heat.

The subject was continued.
Adjourned.

THOMAS D. STETSON, Secretary.

AMERICAN INSTITUTE POLYTECHNIC ASSOCIATION,

January 2, 1863. The Chairman, S. D. TILLMAN, Esq., presiding. Mr. J. H. Churchill read a paper on the artificial formation of saltpeter.

Dr. R. P. Stevens made some remarks on the newly discovered lead mines in the Shawangunk grits, Orange county, N. Y.

The history of the mine is briefly this: In grading for the New York and Erie railroad down the slope of the Shawangunk mountain, from the summit at Otisville to the level of the Delaware river, at Port Jervis, nearly midway of this descent, and opposite the village of Cuddebackville, in the Neversink valley, the workmen made discoveries of boulder lead, or masses of lead ore lying in the earth covering the slope of the mountain. Though the specimens were rich and wonderful, they excited little more attention than to amuse the curious. Some years later, in building a mountain road, the Messrs. Guamaers found other and richer specimens. Some of these were brought to this city and exhibited to mineral men. This exhibition led to an examination of the locality, which speedily resulted in the discovery of the richest lead mine yet opened in the whole range of these mountains, extending as they do from Tennessee to the North river.

You will better understand the peculiar features of this mine, after I shall give a brief geological description of the Shawangunk mountains.

These mountains stretch across the southeastern corner of our State, from near Rondout, to the New Jersey line, at Port Jervis, in a S. S. W. direction. The following great geological formations compose their balk, first; on the east, and forming the main mass of the mountains, lie dark brown and blackish colored slates, which we should call the Taconic slates of Dr. Emmons, known in our State geological report as the Hudson river group. They are from 3,000 to 5,000 feet in thickness, and, with other members of the group, fill up all the country along the Hudson river from Newburgh to the mouth of the Rondout creek. This slate rock is destitute of minerals.

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