ON THE CONSTRUCTION OF HOOPED CANNON. 65 



constructed with hoops as herein described, will sustain a pressure of more than 

 double that required to throw the ball with 1,600 feet initial velocity. There 

 can be no doubt, then, that, as 44 per cent, above the necessary powder 

 pressure has, through long experience, proved sufficient, in the 32-pounder, to 

 provide for the contingent strains from shock and vibration, 100 per cent, must 

 be more than sufficient to provide against the same contingencies in the 



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14-inch gun ; and, indeed, that 14 inches does not approach the size to which 

 guns may be safely trusted, if constructed upon the principles, and in the 

 manner, herein laid down. 



Although it is hardly to be expected that the preceding method of cold 

 working will impart to the hoops, if made of common iron, the elasticity and 

 tenacity possessed by the wire used in the experiments herein related, yet, by 

 the use of iron of superior quality, I think that that standard may be reached. 

 But, should it be found, in the end, that 10 per cent, must be deducted from 

 the tenacity of the wire, in computing that of the hoops, we shall still find 

 the gun constructed in this way, for all that I can see to the contrary, more than 

 twice as strong as any hooped gun ever yet constructed, of the same materials, iveight, and 

 dimensions ; and, by the use of iron of a somewhat steely character, or of some of 

 the low steels, the standard of the strength of the wire may be much surpassed. 



I cannot conclude this paper without observing, that, although in the Memoir 

 formerly published no particular method of hardening the hoops was pointed out, 

 and thus the process of cold hammering and stretching was omitted, still it was 

 always my intention, whenever I should undertake the manufacture of hooped 

 cannon, to prepare the hoops by some process of condensing and hammei 

 hardening. So fully was I impressed, from my experience in the working of iron, 

 with the importance of thus preparing the hoops, that, in 1862, when I had made 

 an arrangement, with the Massachusetts Committee on the Defence of the Ports 

 nad Harbors of the State, for the manufacture of two hundred large cannon 

 arrangement which was entirely approved by the Executive government of the 

 State, and which failed to be consummated only by the rejection of the appro- 

 priation bill, in the Senate, by a majority of one), I visited several of the large 

 machine-shops in the vicinity to find where I could best procure the construction 

 of the steam hammer and tools for performing the operation herein described. 

 My ideas (which were not then very definite) of the importance of subjecting 

 the hoops, to be used upon cannon, to this condensing and hardening process, 

 have been fully confirmed and defined by the experiments herein detailed ; and 

 the conclusions that I have drawn from these experiments will, I think, be 



