1864.] ^5g [Knap. 



descriptions of whicli were given in the Philadelphia Press, of Feb- 

 ruary 12th or 13th, 1864. 



The gun was cast on February 11th, 1864, from three large fur- 

 naces, containing 80 tons of iron. It was cast hollow, and cooled 

 by means of a stream of cold air forced through the bore from an 

 ordinary fan. Air was preferred to the usual stream of water, on 

 account of the great size of the mass, which increased the danger of 

 creating a dangerous amount of shrinkage. The second twenty inch 

 gun, however, made for the Navy, was cooled by water, without 

 injury. 



The cooling occupied two weeks. 



The principal weights and dimensions of the gun are as fol- 

 lows, viz. : 



Rough weight, 160,000 pounds. 



25 feet, 8 inches. 

 66 " 

 48 " 

 19 " 



. 116,497 pounds. 



20 feet, 3 inches. 

 210 " 

 64 " 

 34 " 



" length, 



'' maximum diameter, 

 " minimum " 

 " diameter of bore, , 

 Finished weight, 



^' extreme length, . 

 " " " of bore, 



" maximum diameter, 



" minimum " 



" length of elliptical chamber of bore, 15 " 



The trunnions were set over the centre of gravity of the gun. 

 All of the calculations of weights and centre of gravity, made by 

 Major Rodman, and verified here, proved from the results to have 

 been extremely accurate. 



The iron used was all made in Blair County, Pennsylvania, and 

 was the best quality of warm blast charcoal pig, remelted once into 

 second fusion pigs, from which, the gun was made. 



Specimens from the head gave a density of 7 31 and a tenacity of 

 36,000 pounds per square inch. A specimen from the breech jour- 

 nal gave a density of 7.3715 and tenacity of 43,746 pounds per 

 square inch. The density is taken with distilled water, and reduced 

 to the common comparative standard of 60° F. 



The cost was about $32,000 ; others could be made much cheaper. 

 From the commencement of the first preparations to the comple- 

 tion of the recent trial at Fort Hamilton, New York, not a single 

 error or mishap has occurred, to mar the complete success of this 

 last enormous stride in advance of all experience in Artillery. 



