MECHANICS AND USEFUL ARTS. 65 



of the ship. Mr. J. Nasmyth expressed his opinion that for armor-plates 

 to answer the end for which they were designed, they must be backed 

 by some elastic substance, and, in his opinion, that best adapted to give 

 the requisite elasticity was compressed wool. As Mr. Maury was present, 

 he should like to have his opinion on the subject of cotton, and 

 whether it had been found to answer so far as his experience went. 



Mr. M. F. Maury, late an officer in the U. S. Xavy, said he had not 

 had an opportunity of gaining a great deal of experience on this sub- 

 ject, nor had he had an opportunity of witnessing the experiments that 

 had been made upon cotton. There had been experiments to test the 

 capability of cotton to resist cannon-balls, but the results had by no 

 means been satisfactory. He thought that, cotton had got a false repu- 

 tation. In the early days of the American difficulty, they thought that 

 cotton could resist balls successfully ; but when it came to" the test, they 

 found the bales did not answer the purpose. Mr. J. Scott Russell said 

 the whole course of experience had been to show that they must arrest 

 and shatter the shot at the earliest possible moment, and in the short- 

 est space of time when it struck the armor. 



New Vent-holes for Artillery. A series of experiments have been 

 made during the past year at Shoeburyness, Eng., by the British Ord- 

 nance Committee, to ascertain how far a method now rather in favor 

 among French artillerists, by which a series of holes, about an inch in 

 diameter, are bored through the substance of the cannon near its muz- 

 zle, in order, by permitting a quick escape of gas, to diminish its recoil, 

 aifects the service of the piece as to range and accuracy. The experi- 

 ments were made with two brass 9-pounder ordinary smooth-bore 

 fieldpieces, which were loaded with the usual service charges, and 

 spherical shot. Five rounds were fired from each gun in succession, 

 the recoil of both being carefully measured after each discharge. They 

 were then shifted, so that each occupied the platform which had been 

 used by the other, when again more rounds were fired. The general 

 merits of the performances of each gun were exactly what were antici- 

 pated before a shot was fired. The recoil of the ordinary gun was, in 

 round numbers, just twice as great as that which had the holes bored 

 round the muzzle, while the range and accuracy of the latter were 

 scarcely more than half as good as those of the common piece. The 

 lateral escape of gas and flame through the side holes of the French 

 gun, if we may so call it, was very great indeed, so much so as to prove 

 at once that even if the gun otherwise possessed the most transient 

 merits, it could never be used either on shipboard, in casemates, or even 

 at embrasures. In the open air the trigger had to be pulled by a lan- 

 yard nearly twenty yards long. One half of the force of the explosion 

 evidently escaped through the side holes before the force of the powder 

 was expended on the shot, and virtually, therefore, the barrel of the 

 gun is shortened by as much of its length as is thus perforated. As a 

 general rule, the recoil of the gun is always in e:#iet proportion to the 

 force it exerts in propelling the shot, and anything which takes off 

 from this reooil, by allowing the gas generated by the explosion to es- 

 cape before it has done its Avork, just diminishes by so much the range, 

 and therefore the accuracy, of its fire. The results obtained with this 

 curiously-bored gun were enough to satisfy the Ordnance Committee 

 that the device in question was of no value. 



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