164 ANNUAL OF SCIENTIFIC DISCOVERY. 



attempts have been made in hundreds of forms, no one has succeeded in pro- 

 ducing a cannon essentially more powerful than those used in the days of 

 Napoleon and Wellington. 



I propose, in this paper, to search for the causes of these- failures, to 

 examine the action of the forces, both active and passive, which are called into 

 operation in throwing shot and shells by gunpowder, and, at last, shall 

 endeavor to show that our present cannon do not approach the size and power 

 of those that may be constructed. 



I have said that no essential improvement has been made during the pre- 

 sent age in the size of cannon. It is true that they have been increased in 

 calibre from seven up to eight and ten inches, and a few bomb-cannon have been 

 made of twelve inches. But in the use of these the charges are so diminished, 

 to be brought within the limits of safety, that the initial velocities, as inferred 

 from their short ranges, are not so great as those of the old forty-two pound- 

 ers ; while with mortars, those of thirteen inches were used in the time of 

 Tauban, and this remains, stereotyped, as the limit at the present day. 



But to my examination. The properties or qualities of hardness and of 

 tenacity or strength are the qualities indispensable to all cannon, and the 

 superiority of one cannon over another is measured by the excess in which it 

 possesses them. Inertia* is likewise required in a certain amount, to prevent 

 excessive recoil. Now these properties of strength and hardness are possessed 

 in an eminent degree by bronze and cast iron, and these bodies alone consti- 

 tute in practice the materials for cannon ; for although various attempts have 

 been made to introduce steel and wrought iron, it is enough for my present 

 purpose to say. that there are not twenty cannon in use in the world that are 

 not made of bronze or cast iron. For strength, bronze is generally taken at 

 30,000 pounds to the square inch ; that is, it will require a weight of 30,000 

 pounds to tear asunder a bar of good gun-metal bronze of one inch area. 

 Following the mean of many experiments, cast iron has generally been taken 

 at 20,000 pounds. But that I may be sure not to under-estimate the strength 

 of this material, and as it has been considerably improved by gun-makers 

 within a few years, I shall estimate it at 30,000 pounds, or as equal to bronze, 

 although it is not to be relied upon as so constant in its strength as the latter 

 material. For hardness cast iron greatly exceeds bronze. This renders it 

 more suitable for very large guns, and it has, in truth, become so exclusively 

 the material for everything above the size of field pieces, that I shall deal with 

 it alone in the examination proposed in this paper. 



Before examining the force of gunpowder it may be well enough to say a 

 word upon the time of its explosion. Is the firing of gunpowder instanta- 

 neous ? If it be instantaneous, then it must be evident that no other sub- 

 stance can be fired with a greater rapidity. For instantaneousness, bearing 

 the same relation to time that a point does to space, can admit of no degrees. 

 Both are existences without extension, and we cannot say of any two events 



\ 



* This word is used throughout this paper in its strictly technical sense, as the force, or 

 power of resisting all change of state, whether it be from rest to motion or from motion 

 to rest ; and I use, without a doubt of its accuracy, the square of the velocity by the mass, 

 as the measure of this force. 



