138 PROCEEDINGS OF THE AMERICAN ACADEMY 



foot high (32 X 40,000), if we divide this product, representing the 

 strength of the whole gun, by the weight of the metal of which the 

 gun is made up in pounds, we shall obtain the strength, or work which 

 may be done by each pound of which the gun is constituted. We 

 shall find the result of this computation (the weight of our standard 

 32-pounder being 7,500 pounds) to be (J-SJinJ/a = 171) 171 pounds, 

 in shot, raised one foot high by every pound of metal which forms the 

 body of our standard gun. 



By this form of computation we may compare, numerically, the 

 strength of one gun with another, and assign to each the true value 

 derived from its peculiar metal, or the method employed in its con- 

 struction, free from all adventitious sti'ength that may be supplied by a 

 mere increase of mass or quantity of material. The accuracy of the 

 result will of course depend upon the experimental determination of 

 the weight of the shot and the velocity which the gun may be relied 

 upon to enable us actually to produce and practise, without exceeding 

 the limits of the strength of the gun. 



Dahlgren. 

 I now proceed to the application of these forms of computation to 

 the guns now most relied upon in the American and English service. 

 First the cast-iron ten-inch gun known in this country as the ten-inch 

 Columbiad, and described as follows : — 



Diameter of bore, 10 inches. 



Weight of gun, 15,059 pounds. 



Weight of shot, 128 " 



Charge of powder, 18 " 



Initial velocity of shot, 1,044 feet. 



From these several elements the following results are obtained by the 

 mode of computation before pointed out. 



Height to which the shot will rise if pointed directly upward, in vacuo, 17,030 



feet. 

 Force in pounds raised one foot high, 2,179,840, 

 Force compared with the 32-pound shot under a velocity of 1,600 feet a 



second, this being taken as 1, 1.7. 

 Force in number of horses working one minute of time, 66.2. 

 Number of pounds (in shot) raised one foot high, by each pound in the 



weight of the gun, 144.7. 



Rodman. 

 Passing from this to the giant of the service, the Rodman fifteen- 

 inch gun, which gives the following elements to be subjected to com- 

 putation : — 



