892 FRAGMENTS OF SCIENCE 



timies; the motion of the mass is converted into a motion 

 of the atoms of the mass; and these small motions, com- 

 municated to the nerves, produce the sensation we call 

 heat. 



We know the amount of heat which a given amount of 

 mechanical force can develop. Our lead ball, for exam- 

 ple, in falling to the earth generated a quantity of heat 

 sufficient to raise its own temperature three-fifths of a 

 Fahrenheit degree. It reached the earth with a velocity 

 of 32 feet a second, and forty times this velocity would be 

 small for a rifle bullet; multiplying gths by the square 

 of 40, we find that the amount of heat developed by col- 

 lision with the target would, if wholly concentrated in the 

 lead, raise its temperature 960 degrees. This would be 

 more than sufficient to fuse the lead. In reality, how- 

 ever, the heat developed is divided between the lead and 

 the body against which it strikes; nevertheless, it would 

 be worth while to pay attention to this point, and to as- 

 certain whether rifle bullets do not, under some circum- 

 stances, show signs of fusion. 1 



From the motion of sensible masses, by gravity and 

 other means, we now pass to the motion of atoms toward 

 each other by chemical affinity. A collodion balloon filled 

 with a mixture of chlorine and hydrogen being hung in 

 the focus of a parabolic mirror, in the focus of a second 

 mirror 20 feet distant a strong electric light was suddenly 

 generated; the instant the concentrated light fell upon the 

 balloon, the gases within it exploded, hydrochloric acid 



1 Eight years subsequently this surmise was proved correct. In the Franco- 

 German War signs of fusion were observed in the case of bullets impinging on 

 bones. 



