L. MECHANICS AND ENGINEERING. 479 



HEAT AND PRODUCTS OF GUNPOWDER EXPLOSIONS. 



According to recent experiments by Captain Noble and 

 Mr. Abel, the temperature of the explosion of gunpowder, by- 

 means of platinum wire or tin-foil, is about 2200 C. The 

 products of explosion consist of about fifty-seven parts, by 

 weight, of solids, to forty-three of permanent gas. When 

 the powder fills the space in which it is fired, the pressure is 

 about 6400 atmospheres, or 42 tons to the square inch. The 

 products of explosion generally are the same in a gun and in 

 a completely closed vessel, w^hile the work on the projectile 

 is due to the elastic pressure of the permanent gases. 3 A, 

 Nov. 21,1874,66. 



EXPLOSIVE AGENTS. 



The report of Professor Abel on explosive agents as ap- 

 plied to industrial purposes, delivered to the Institution of 

 Civil Engineers, and the discussions thereon during the past 

 three years, have been recently published in a pamphlet, from 

 which the following facts are taken. 



Passing from the consideration of gunpowder to those 

 substances that have been proposed as substitutes therefor, 

 Professor Abel considers the three principal ones as picric 

 acid, nitro-glycerine, and gun-cotton. 



Nitro-glycerine has been raised from the position which it 

 held for sixteen years, as a rare and apparently useless chem- 

 ical, to that of a most important industrial agent, through 

 the skill and perseverance of Mr. Noble, w r ho, in 1863, made 

 public his proposition to add to the explosive power of gun- 

 powder by impregnating the grains with nitro-glycerine. 

 In 1864 Mr. Noble described several methods of exploding 

 charges of nitro-glycerine, and showed that the explosion 

 takes place w 7 ith such great rapidity that it is unnecessary 

 to confine the charge by tamping or any other means. Nh 

 tro-glvcerine is now extensively employed, not only in Cali- 

 fornia, but in Sweden, Germany, and Wales. The poisonous 

 nature of the exploding gases, which injuriously affects the 

 health of those handling it, is one of its defects. The mate- 

 rial is much less susceptible to accidental detonation in the 

 frozen than in the liquid condition. The accidents which 

 have occurred with frozen nitro-glycerine appear to have 



