PROCEEDINGS OF THE. POLYTECHNIC ASSOCIATION. 663 



from the generated heat, and still a third loss by friction in using 

 the compressed air. 



The report was accepted and ordered on file. 



PROJECTILES RIFLED CANNON. 



Mr. Babcock resumed his remarks upon the results attained by 

 the shot invented by Gen. James. He objected to the shot, first, 

 on account of its necessary want of accuracy. The belt of soft 

 metal around the shot flies off as it leaves the gun, in consequence 

 of the expansive force of the gases ; and unless this belt should 

 separate into equal pieces, their reaction would necessarily turn 

 the shot from its course. If these pieces could perfectly balance 

 each other, the reaction would be balanced ; but this does not occur 

 in practice, and therefore the ball must necessarily deviate from 

 its true trajectory. The results attained confirm this statement. 



Mr. B. exhibited a sketch of the target at "Watch Hill, R. I., 

 13 by 17 feet, placed at a distance of 2,000 yards from the gun. 

 Sixty-five shots had been fired with 80-pound shots, and there were 

 but ten marks upon the target, a portion of these having been 

 produced by ricochet hits. Captain Dalhgren, in an official report 

 made last December, compares the results which were attained 

 by trials in the Navy Yard, at Washington, of other rifled can- 

 non with the results attained by the Board of United States 

 Artillery Officers appointed to test General James' projectile, 

 giving the preference to the former. The next objection is that 

 General James' shot is deficient in penetration. This Mr. B. 

 attributed to the honey-comb structure of the rear of the shot, 

 causing a serious resistance to the atmosphere. No man would 

 make the stem of a vessel in such a form. In the experiments 

 upon Watch Hill, it was claimed that one shot had passed through 

 52 inches of oak timber. This was the only shot which passed 

 through the target. The target was three feet thick, composed 

 of squared oak timber 12 inches square, and tied together; and 

 this shot had happened to pass between these timbers, after which 

 it had passed through a support 12 inches thick, and another 

 target four inches in thickness. The next best shot was imbedded 

 18 inches, the next best 15 inches, and the next best but three 

 inches. In throwing shell upon the deck of a vessel, it would be 

 necessary that the angle of elevation should be considerable. 

 The rotation would have a tendency to cause the line of the axis 

 to remain parallel to itself, and consequently the shell would 

 strike the vessel partially upon its side. 



