Manchester Memoirs, Vol. xlvi. (1902), No. 10. 25 



passive nature of body, as that it never changes its velocity 

 of itself As body has no self-motive power, or spon- 

 taneity, if it were to change its direction, how could it," 

 he asks, " determine itself to any one direction rather than 

 to another?" 



Now, no one will be found to deny that gunpowder 

 nitroglycerin, or other endothermic substance is a body 

 according to Definition I. and Law I. of Newton's 

 Principia. The experiments of Fairbairn, an account of 

 which was read before this Society in 1859,* have shown 

 that gunpowder, under great pressure, becomes a hard 

 compact mass with a smooth and shining surface. Let, 

 therefore, a mass of this explosive, the same weight as 

 the disc of the gyroscope (4*5 lbs.) be pressed into a 

 mould of similar form and mounted on a spindle. Such 

 a disc, or spinning top, to use Newton's illustration, would 

 exhibit all the phenomena of rotation, qualitatively and 

 quantitatively, as if it were formed of gun-metal. If now, 

 when the disc is in rapid motion, an electric spark be 

 transmitted from a conductor through the disc, the rotatory 

 motion of the body will be suddenly arrested, not by 

 external mechanical impulse, but by its own spontaneous 

 motion, or internal force. In like manner, if the disc or 

 other endothermic body were projected upwards through 

 the air by some mechanical means, at the rate of 100 feet 

 per second, and if an electric spark were transmitted 

 through it by wires carried by the body during its ascent, 

 the upward motion would immediately cease, and the 

 molecules of the body would project themselves, spon- 

 taneously, in every direction as in the case of the rotating 

 endothermic disc. Moreover, the molecular motions of 

 the gaseous products, created by the explosion, would 

 continue active for an indefinite length of time, until 

 these products entered into new chemical combinations. 



* Proc. Lit. and Phil. Soc. Manchester, Vol. I., p. 117. 



