ANNUAL OF SCIENTIFIC DISCOVERY. 



lengths of bore, the effect upon the gun itself at different parts of its length, and 

 various other grounds of comparison, I think that we may take the effect of the 

 charge through the whole bore, supposing it to be 112 inches from the bah 1 to the 

 muzzle, and the charge 80 pounds, as equal to the action of the maximum force 

 through a space of not less than one half, nor more than two thirds of its 

 length. But that I may be sure to assign the maximum so great as to cover 

 ah 1 anomalous or accidental conditions, I will take it as sufficient to produce 

 a velocity of 1,600 feet a second, if acting constantly through one third the 

 length of the bore. This will give 37^- inches, or exactly 4 tunes" the length 

 of the cylinder which forms the equivalent of the shot. Then (from the 

 formula v = Vfs) the 40,000 feet above given for the height of the column, 

 becomes ^ = 10,000 feet; and if we take the whole force of the powder 



as equal to its maximum force, acting through two thirds the length of the 

 bore, or 74 inches, our column will become 5,000 feet high. In all cases 

 of providing strength, we must take the force to be resisted at its maxi- 

 mum. 



Now a bar of cast iron 1 inch square weighs 3'2 pounds to the foot in 

 length : we have then 10,000 x 3'2 =c 32,000 pounds pressure to each square 

 inch of surface, or 3 2 " = 2,133 atmospheres, on the supposition that the 

 whole action of the powder is equal to its maximum force through one third 

 the bo: o of the gun. If we take the whole action as equal to its maximum 

 through two thirds of the bore, the column, 5,000 feet high, gives 16,000 pounds, 

 or 1,06G atmospheres. It cannot be less than this, and although it may never 

 come up to the greater number, or 2,133 atmospheres, it would not be safe 

 to estimate it at less when providing the means to resist it. We require, 

 then, a pressure of 32,000 pounds to the inch, to obtain for a 14-inch shot an 

 initial velocity of 1,600 feet a second. We have seen that a gun formed as I 

 have proposed will be capable of resisting a pressure of 63,960 pounds to the 

 inch, or very nearly twice the pressure required to produce the velocity 

 sought, while with a gun made in the usual way, of one piece of cast iron, the 

 power of resistance is limited to 20,000 pounds to the inch, or less than two 

 thirds that which may be required to obtain the velocity. 



"We have seen that a cannon constructed in the manner recommended, of 

 whatever size, having its walls equal in thickness to the diameter of its bore, 

 will sustain a pressure of 63,960 pounds, equal to a column of fluid iron 

 20,000 feet high, very nearly. This is half the strength required to support a 

 column capable of keeping up a continued stream with a velocity of 1,600 

 feet a second. Suppose that we construct such a cannon with a bore of 30 

 inches, and of such length that the ball shah 1 receive the force of the powder 

 while it moves through a space of 10 feet, and that this force be equal to a 

 constant action of 4,266 atmospheres through 40 inches: it will be* at once 

 perceived that it will impress the above velocity upon a cylinder |^= 20 

 inches long, or upon its equivalent, a sphere 30 inches in diameter. Such a 

 sphere of solid iron will weigh 3,670 pounds, and at this point the calculated 

 power of the gun meets the force required to give a velocity of 1,600 feet a 

 second. 



Although this size may be beyond practical reach, the contemplation of it 



