"At present there is a great excitement in Mariposa, from the recent discovery of very valuable silver and gold veins, which thus far surpass in richness any heretofore found. Large quantities of the ore have been sent to San Francisco for assay. The silver has turned out at the rate of $500 per ton; the gold much beyond that figure; and, as they dig down, the richer it becomes. Speculators from San Francisco are here in squads, buying up the various interests. The discoverer is entitled to 500 feet of front, running back as far as the vein extends; all other claimants are entitled to 250 feet, and as it requires a large outlay of money to construct mills and machinery, none but great capitalists can profit much by this discovery, except by selling their interests to the best advantage to others, and in this way large fortunes are being made. My sons have some valuable claims."

to

The regular subject, "Iron-plated Ships," was then taken up.

Mr. Fisher. As I proposed this question, I suppose it devolves on me open the discussion with the remarks that I have to make. It has been found, in England, that solid plates are better than armor made of several thin plates. If the plate is solid and the iron is good, the force is expended in altering the form of the shot, but if the plate is weak, that gives way, and the form of the shot is not changed. It has been found that wrought iron shot is not as good as cast iron, and it is now proposed to make the shot of steel. The main office of these plates is to keep out shells, as solid shot are not very destructive. Mr. Whitworth has sent a shell through a target like the side of the Warrior; the shell passing through the plate and bursting in the target, tearing it to pieces. The novel thing about this shell was, that no arrangement was prepared for exploding the charge; it was fired by the concussion of the projectile as it struck. It could accordingly be handled with perfect safety, as dropping it, even into the hold of a vessel, would not cause it to explode.

Mr. Dibben.-What, then, caused it to explode when it struck?

Mr. Bartlett.-This is one of the manifestations of the conservation of force. The heat is generated by the destruction of motion. The mechanical force or motion is converted into caloric.

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Mr. Dibben. These target experiments are calculated to mislead, from the fact that the conditions under which they are made are very rarely realized in practice. The gun is placed in a position exactly at right angles with the target, the distance is short and is accurately known, and consequently the penetration or destruction is much greater than it would be in actual warfare. I think the plates yet have the advantage of the guns. No practically successful wrought iron guns as large as 100-pounders have ever been made in any considerable numbers, and the best gun yet manufactured is the Parrott, or some one made on the same plan-that is, a cast iron core with bands of wrought iron. Mr. Parrott has made a large number of 200-pounder rifled cannon, and three which fire his shot. weighing 300 pounds, and the proof of all of these guns has been eminently successful; the charge for the 100-pounders is one-tenth the weight of the shot, but that for the 300-pounders is a little less than one-tenth. So confident are Mr. Parrott and his men in the strength of these guns,

that in trying the first proof they stand in the immediate vicinity of the gun when it is fired.

The subject of "Recent Improvements in Warfare" was chosen for the next meeting, and the Association adjourned.

THOMAS D. STETSON, Secretary.

AMERICAN INSTITUTE POLYTECHNIC ASSOCIATION,
December 11, 1862.

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The Chairman, S. D. TILLMAN, Esq., presiding.

A communication was read from the secretary of the board of managers, in relation to articles entered for premiums.

On motion, the time for receiving articles for premiums was extended to the 18th December next.

LAMP FOR BURNING OIL WITHOUT A CHIMNEY.

Prof. Seely read the following communication from Mr. B. Woodard, of Buffalo, New York, dated December 1, 1862:

I notice that at the meeting of the Polytechnic Association, on 23d October last, you had under consideration a lamp for burning oil. In experimenting with petroleum, I have hit upon a device for burning rock oil, either refined or crude, equally well, without a chimney and without smoke or smell, except when extinguished, and for a few moments after. Take a common single tubed night lamp used for fluid, and prick three holes through the cap into the body of the lamp; make the holes near enough to the tube to come inside of a petticoat, which can be made of tin, and soldered air tight to the cap, and come up flush with the top of the wick (a trifle above the wick tube). Have the petticoat large enough to leave just double the space or bore there is to the wick tube, and it will burn petroleum or other oil, camphene fluid, or other combustible fluids equally well, and is non-explosive..

It is a simple contrivance, but if you think it worthy of your attention, I would like to have it brought before the Association for their consideration. P. S. I should have added, there is to be no vent to the lamp, other than through the three holes between the petticoat and wick tube. The experiments may be made more interesting by enlarging the lamp, tubes, wick, &c., and make the petticoat of transparent glass. The accumulation of smoke, gases, &c., can then be seen confined within the petticoat, and also its combustion.

A saving of 2 per cent. is effected, and the lamp always clean.

PLAN FOR ENLARGING LOCKS ON CANALS.

Mr. Bull introduced Major Taylor, who proceeded to explain and illustrate, by model, his plan for enlarging locks of canals by a new construction of the gate.

A drop gate, much outside of the present gate, is to be employed on the

upper side, and a peculiar swing gate, swinging opposite to the usual direction, is employed much outside of the usual one on the lower side. The total addition to the length is some 50 per cent., and gained at a small cost. The present practical length, i. e., the length of boat passed, is but 97 feet with the present locks; the length to be passed with the new gates at both ends is intended to be 150 feet and some inches.

The cost of fitting one lock with these devices would be, as estimated, about 2,500 dollars. The cost of enlarging a lock to an equal extent, by masonry, would be about ten times that amount.

The regular subject of the evening, "Modern Improvements in Warfare," being called by the Chairman,

The Secretary introduced to the meeting Mr. Norman Wiard, widely known as a successful inventor, experimenter, discoverer and manufacturer of ordnance, and as the author of a series of improvements which had been submitted to the attention of the government, and which he was now prepared to place before this Association. Mr. Wiard was distinguished for presenting or elaborating in drawing to the minutest details his various inventions, while many are satisfied with presenting their schemes in general and crude outline. This difference in method in every light is very obvious, and it both enables and entitles Mr. Wiard's statements and suggestions to receive careful consideration.

GREAT GUNS.

Mr. Norman Wiard. It is a matter of public concern, that although > much time, money and ingenuity have been expended in efforts to produce safe and effective ordnance of large calibers, no large gun has ever been designed or made that could be pronounced entirely trustworthy, even after it had been subjected to the usual test of firing, a process exposing the gun to destruction and imperiling the lives of the gunners and inspectors; for after enduring any prescribed number of trial charges, there is no certainty that the gun will not burst at the next round. Numerous examples could be quoted to show that large guns have burst with a small charge after having withstood a succession of heavy charges.

Cast iron guns, with a tensile strength of 16,000 lbs. to the square inch, have exhibited greater endurance than others of the same size and model having a tensile strength of 38,000 lbs.

Experts have found themselves unable to account for the fact that a large steel gun, with a tensile strength of 120,000 lbs. to the square inch, exhibited less endurance than a cast iron gun with a tensile strength of but 30,000 lbs., or that the strongest metal does not make the strongest gun.

By examining the fragments of guns of ordinary forms which have been burst, it will be observed that they burst in three ways:

First. They split through the cascabel and re-enforce longitudinally to a

point forward of the trunnions, and from thence the fracture diverges to either side, leaving the chase and muzzle unbroken. Sometimes cross fractures through