OF ARTS AND SCIENCES : NOVEMBER 14, 1865. 49 



the internal compressed portion to attain its normal condition before 

 this internal portion (which is the first to break in the common gun) 

 is subject to any strain at all. It will be perceived that if this prin- 

 ciple could be rigorously applied, a cannon could be made so perfect 

 that, when subjected to a bursting pressure, every fibre, from the inter- 

 nal to the external surface would be at that instant equally extended, 

 each contributing its full share of resistance to fracture. The whole 

 resistance would be proportional to the area of fracture. 



This was supposed to be the case in common cylinders, before the 

 error was pointed out by Barlow, and also by Lamie and Clapeyron. 

 And it was this erroneous supposition that led Count Rumford to his 

 exaggerated estimate of the force of gunpowder, as tested by its power 

 of bursting gun-barrels. If he had used the theory which gave origin 

 to the hooped gun, his results would nearly have agreed with modern 

 observations. 



The demonstration of the superiority of the hooped gun, with detailed 

 directions for its construction, is contained in a paper read before this 

 Academy in February, 1856, and published at the beginning of the 

 sixth volume of our Memoirs. This was the first published account of 

 the invention, which had been patented nearly a year before. Captain 

 Blakely's pamphlet, published in England in 1858, sets forth the ad- 

 vantages of this construction by similar arguments ; as also does an 

 elaborate paper read by Mr. Longridge before the Institution of Civil 

 Engineers in February, 1860. Both these gentlemen, however, were 

 engaged in researches upon this subject at an earlier date, but not so 

 early, it would appear, as was Mr. Tread well. 



The validity of the principle, and the soundness of Mr. Treadwell's 

 views upon the whole subject, as set forth in his memoir, have been 

 amply confirmed by special experiments made in England with the 

 Blakely and Whitworth guns, and by experience in this country dur- 

 ing the last four years with the Parrott and the Blakely guns. 



It must not be supposed that the earlier invention is superseded by 

 the later one. That is used in forming the hoops of the Parrott gun, 

 and in most of the British guns. And the best gun which could now 

 be made, as experience has shown, would be composed of a barrel of 

 cast-iron or steel, enclosed and compressed by a cylinder of coil. 



We need not discuss the question of priority of invention between 

 Mr. Treadwell and others, competitors for a share in the honor of pro- 

 ducing the modern cannon. His independence of each and all of them 

 VOL. VII. 7 



