this is another cause of the retardation to its motion outward. Although for ninety-nine hundredths of the whole time the heat is radiating from the surface of the bore, the velocity with which it leaves is much less than the velocity with which it is received, because the difference in the temperature of the gun and the atmosphere occupying the bore is much less than the difference of temperature between the metal of the gun and the Fig 13. gases ejecting the shot by their pressure. The atmosphere occupying the bore receives the heat by radiation, in the intervals between firing quickly from the immediate surface, and less quickly a little distance beyond; and so again the heat flows from the metal of the gun with reduced velocity as the distance increases from the bore, leaving the point of highest temperature in the mass of metal, but not far from the surface of the bore. (See Fig. 13.) Its effect toward causing rupture may be illustrated by taking a cylinder of pine wood a few inches in length and a crosssection like the diagram, and providing a wedge similar in form to a bayonet, but truly tapered to a point from a cross-section at the head, the same as the lines representing the place and quantity of heat on the diagram, showing its effects by intermittent communication of heat. (Fig. 13.) If the point of this wedge be set upon the end of the wooden cylinder at the point supposed to be the point of greatest heat, according to the theory above, and by a blow driven into the end-wood, it will penetrate so as to make an impression like the inner line of the diagram. A second blow, driving it further into the wood, penetrating as if to the second line of the diagram, and expanding the wood, will cause a fracture inward toward the surface of the bore, first; a third or fourth blow will split it to the outside. And thus guns burst, the first fracture occurring on the inside, and afterward opening to the outer surface. Mr. Edward Cooper was of opinion that guns generally burst through the vent. The question was continued to the next meeting, and that of "Inland Navigation" was selected for the 9th of January. Adjourned. THOMAS D. STETSON, Secretary. AMERICAN INSTITUTE POLYTECHNIC ASSOCIATION, The Chairman, S. D. TILLMAN, Esq., presiding. Mr. Stetson, the Secretary, exhibited to the meeting specimens of the fiber of Sisal hemp, also some of the raw material, green leaves of the cactus species-the Axgave Americana, several feet in length. This material has long been prepared by the Indians of Yucatan, using very primitive apparatus, enabling one man to prepare about four or five pounds per day of fiber. Machinery has lately been introduced, which was explained by Mr. S., for preparing the fiber. He alleged that one machine attended by two men or boys in ten hours would produce 500 pounds, better cleaned than by the primitive process. He believed it was a fiber entitled to much attention. Some of the waste, a short fiber, was now in the hands of Mr. John Priestly, an extensive manufacturer of this city, and paper from it would be exhibited at a future meeting of this Association. Some fifteen tons of this waste had been recently brought to this port, but for what purpose or price, he Mr. S. had not learned. He believed the machine described, which was the invention of Mr. E. I. Patrulla of Merida, an extensive cultivator of this material, was a curiosity as a very marked example in which extreme simplicity and great economy of production had been reached through experiments with more complex and inferior apparatus. The machine now is little more than a drum with teeth, running in a tight case. The Chairman. I have the pleasure of introducing to the meeting Mr. Hyslop, who will make some remarks on ventilation, and illustrate the action of air currents in rooms; and conclude by exhibiting Mr. McKinnell's ventilating apparatus, which was several years since patented in England, and is extensively used there. Mr. Hyslop after some remarks upon the importance of perfect ventilation, proceeded to give a practical illustration of this subject. He showed that an opening in the top of a room, or a pipe of any kind carried from the ceiling to the outside and above the roof, would not alone remove foul air; he placed three lighted candles under a glass shade which had a large opening through the top of it; the oxygen of the air was soon so far exhausted that the lights were extinguished; he next repeated the experiment, placing an open tube upon the opening, such as are commonly used for carrying off foul air from public buildings, and the lights were extinguished as before; he then relighted the three candles and placed them under the glass shade and about three inches apart, in the form of a triangle; he fixed an open tube in the opening on the top of the shade, and raised the lower edge of the shade on one side, by putting the point of a pencil under it, opposite the center light; this admitted a free current of air, which came in at the bottom and went out through the tube at the top; the effect of this was that the light opposite the opening made by the pencil was kept burning brightly, but was agitated by the draught, whilst the lights on each side of it were extinguished by the deficiency of oxygen in their locality; he argued from this experiment that the lower part of a room was the wrong point at which to admit fresh air, as it passed through the room without diffusing itself, causing inconvenient draughts where it went, and leaving some parts unvisited. He then covered the opening in the top of the shade and placed three lights in it at different levels; one near the top, one at the bottom, and one about midway between the other two; no change of air was allowed, and as the carbonic acid began to accumulate the lights were extinguished; the highest first and the lowest last. Mr. Hyslop showed by this that carbonic acid ascended to the ceiling, and accumulated downward from that point when it was not allowed to escape, the upper part of a room always being most impure. He next exhibited a model of Mr. McKinnell's patent double current ventilator, in operation. The ventilator consists of two tubes, one within the other, leaving a space between them; the inner tube is the longer, and projects above the outer tube at its upper end; both tubes terminate at their lower ends on a level with the ceiling, but fitted inside the bottom of the inner tube is a short sliding piece, to the lower edge of which is attached a circular flange, which projects outward parallel with the ceiling, and conceals the opening of the outer tube when viewed from below; both tubes are properly protected on the outside by cowls. The action of the ventilator is as follows: The greater length of the inner tube determines the upward current to take place in it; it therefore becomes the foul air shaft; the outer tube becomes the fresh air inlet, and the descending current striking against the flange is thrown out on the plane of the ceiling, and so diffused; by the use of valves the action of the ventilator can be increased or diminished at pleasure. The ventilator was fitted into the hole in the top of the glass shade, which was used to represent a room; a piece of thick blotting paper was lighted and then the blaze blown out, and the smoking paper held outside the fresh air entrances; the descending current of fresh air took in with it the smoke, which showed the course of the air as it passed inward and over the flange, which threw it out equally in every direction, passing down by the sides of the shade and finally passing upwards in the center, making its escape up the outlet pipe as foul air; a candle was kept lit under the shade, which burnt brightly, but without any agitation such as would have indicated an inconveniently strong draught. A modification of the same plan of ventilation was next exhibited, which showed how the lower rooms of houses might be ventilated without the rooms above them being interfered with; the fresh air is brought in from the side of the house by pipes laid horizontally betwixt the beams in the floor above the room ventilated, and is diffused from the ceiling in the center of the apartment; the foul air is carried along horizontally in the same way, to the outside wall, and the pipe is then carried up vertically in the wall for a few feet, or in some cases to the top of the house, and the air then allowed to escape. Mr. Hyslop was listened to with great interest, and some of his experiments elicited hearty applause. Mr. Fisher then explained, by means of diagrams upon the blackboard, the patented balance piston valve of T. S. Davis, as applied to locomotives. Unlike ordinary pistons, the head and follower are of considerably less diameter than the ring, which is counterbored to receive them. The width of the ring is equal to the entire thickness or depth of the piston, its edges being flush with the outer faces of the head and follower. The latter are held together, and held tightly upon the counterbored shoulders in the packing ring, by being placed on the valve stem, with a nut on each side of the piston. The head and follower are tightened against the inner shoulders of the ring, and not upon each other, for the head does not extend so far through the piston as to allow the follower to take its bearing upon it, The cast iron ring is cut open at a single point, the cut being made square across the face of the ring, and of such shape as to receive a dovetailed key which may be set up by a screw so as to expand the ring, and bear on its outer face against the inner surface of the cylindrical steam chest in which the valve moves. The steam ports extend around the whole circumference of the steam chest, and admit steam at their outer ends only. The valves are necessarily balanced, and work with hardly any friction. From their construction, the ring cannot be blown in, or reduced in diameter, by the direct pressure of the steam, when the piston is opposite the steam port; nor can it expand outward, except as it is forced open by direct pressure in screwing up the dovetailed key, and the length of the pistons in proportion to the width of the posts is such that no blow or shock occurs as the pistons pass the ports. An objection to piston valves has been urged in former times, that from unequal expansion of the valve they would stick, but in Mr. Davis's plan the steam first surrounds the inner case in which the valve moves, and becoming heated before the valves, renders it impossible for them to become fastened. The regular subject, "Improved Modes of Modern Warfare," was then taken up. Mr. Geo. Bartlett exhibited and explained the Burnside rifle, invented by Major-General Burnside. It was just brought out, and very highly approved, after trials before a commission in the year 1857-8, but the manufacture did not succeed well. Since the commencement of the present war it had been again renewed, and a company in Providence are now making about 2,000 per month. The arm was preferred, for cavalry use, to any other. Dr. Rich asked why this was superior to other breech loading arms. It seems to have been so pronounced by the commissioner of army officers. Mr. George Bartlett.-I believe it is mainly ascribed to the solidity with which its parts were applied together. I do not know how fast it could be fired, evidently not so fast as those which carry the percussion material in the cartridge; this is used with separate caps. Mr. F. Dibben said rapidity of fire was not as important, for war purposes, as accuracy, durability, strength, or force of its shooting. The Burnside rifle excelled in these, and especially in the provision for plug tightly, at all times, in the barrel. fitting the Dr. Rich thought rapid loading was a very great desideratum. It was certainly no disadvantage to load rapidly even if it was not desired to fire rapidly. Mr. George Bartlett said this was a good target rifle, the only one, he thought, of the breech loading class, which had worked well for such purpose. The Secretary said the difference in time of loading, between the common muzzle loading and any breech loading arm, is much overrated. He had, on a test trial, loaded and fired four times at a target in less time than a friend had operated a breech loader at his side. He had found Mr.. Lewis, president of the National Rifle association, in favor of muzzle loading pieces alone. Mr. Norman Wiard said a great advantage in the breech loading arm, lay in the greater number of times a piece could be fired without heating. He said much heat was stopped by the copper case, and prevented from striking into the gun. Dr. Rich advocated the kind of arm known as the Maynard Rifle. These, and other breech loaders, have been fired fifteen times per minute. Muzzle loaders cannot be fired as fast. Mr. George Bartlett spoke in favor of the Clark's Patent muzzle, which is applied to cover and protect the muzzle of a rifle while loading. Mr. H. L. Stuart, the associate of Mr. Wiard, stated that all of Mr. Wiard's inventions and improvements in ordnance had been made independent of all assistance or co-operation of the government ordnance authorities, and, in fact, in the face of discouragements and direct opposition on the part of the chiefs of the ordnance bureaus. He said that after a prolonged and careful investigation, he was fully satisfied that no radical or really important discovery or improvement in the method of fabricating great guns had been made by the ordnance bureaus of the army or navy, and that the real cause of their bursting, viz: unequal expansion by the great heat, 6,000° Fah., resulting from the combustion of gunpowder, had never been considered at all by the ordnance authorities. He said that he believed that Mr. Wiard had discovered the true cause of failure, after long study, and a large expenditure of time and money. Mr. E. Stevens thought all the breech loaders would shoot nearer than common soldiers could see; in his opinion either style of gun therefore would do for accuracy. Mr. Stetson called upon Mr. Wiard to explain the mode of taking in the air which he had invented for iron clad vessels, and adverted to the fact that Mr. Wiard does not content himself with merely finding the faults in the vessels already built, but brings out definite plans for remedying them. Mr. Wiard proceeded to explain by diagrams his mode of taking the air through hollow columns and hollow deck beams from a great multiplicity of holes on the deck. Provision was explained for drawing foul air and rejecting either water or the gas from any burning mass presented to any portion of the deck. The exhaling of the air through the wheels or screws encased within the vessel and only projecting through the bottom was further explained. It . would, among other advantages, make the vessel appear less like a steamer, and would appear to be but a sailing vessel. Mr. Wiard proceeded with his remarks, and spoke of "projectiles" sub-. stantially as follows: |