NATURAL PHILOSOPHY. 173 



as a theoretical perfection may stimulate us to attempt an approximation to it. 

 A ball of a ton weight, with a range of, say six miles, would, as a mere dis- 

 play of mechanical force, be worthy of a great effort. 



The following columns show the stress that the several kinds of guns, as 

 mentioned, will bear, by calculation, and the pressure required to give the 

 velocity of 1,600 feet a second. The third column shows the proportion 

 between the required and the actual strength. 



Atmospheres. AUnosplieres. 



Hooped cannon for 14-inch shot \vill bear 4,266; required 2,133 100:200 



Cast iron gun, 14-inch shot, will bear . 1,838; " 2,133 100: 62 

 Cast iron 82-pounder cannon, 6% inches 



thick, will bear .... 1,333; " 920 100:142 



Hooped cannon 30 in. diam. 3,670 Ib. shot, 4,266 ; " 4,2f/6 100 : ICO 



By this it appears that a common cast iron 32-pounder, having but 42 

 per cent, more strength than is required, is less reliable than a hooped gun 

 of 14 inches. It will be recollected that the numbers given above in the 

 second column, as showing the required strength, represent the utmost 

 force ever exerted by a charge intended to produce a velocity of 1,600 feet a 

 second. 



In this paper, my principal object has been to show a mode of construction 

 by which, with our present materials and knowledge, it will be perfectly 

 practicable to make guns of great size capable of standing the requirements 

 of the service. It follows almost of course, that the same form of construction 

 must be the best possible for guns of smaller calibre, and that by adopting it, 

 not only will the use of guns of enormous size be rendered practicable, but, if 

 applied to cannon of smaller size, their bursting will be rendered almost im- 

 possible. If it be necessary to use the word cost in connexion with the object 

 to be attained, I know that when the manufacture is mastered, with a good 

 machine shop, the difference between the last of these and common cast iron 

 guns will be altogether insignificant to the nation. 



I abstain from opening the subject of different forma of bore and of shot, 

 although I believe that in the end some cyhndrico-conical form, lightened with 

 cavities in the rear portion, and perhaps with some form of spiral grooves to 

 produce rotation from the air, will be substituted for the solid spheres now 

 used. 



I should, however, leave the subject of this paper but very imperfectly 

 treated, if I neglected to mention one most important effect of the force of the 

 explosion, which is not indicated cl priori by any theory, and which is so 

 inconstant and uncertain in amount, that it can be appreciated only by a 

 careful observation of its practical effects upon the gun, but which, unless 

 guarded against, must essentially disturb the conclusions which I have herein 

 deduced. I allude to what is known to artillerists as the lodgment or inden- 

 tation of the ball. This first shows itself at the point immediately under the 

 ball, where it rests at the moment of the discharge. It is best observed in a 

 soft bronze or wrought iron gun, and from the first instant of its appearance, 

 as a slight impression of the undej surface of the ball, it goes on increasing at 

 every discharge, until it becomes so deep as to deflect the ball upwards at tue 



