GAS AND GASOLINE ENGINES 11 



7. BLASTING 



If a hole in a ledge of rock, or the stump of a tree, is filled 

 with gunpowder or dynamite packed down with sand, ignition 

 of the powder will cause an explosion and considerable local 

 damage. The solid powder turns instantly to gases, which, 

 due to their nature and the high temperature, occupy an enor- 

 mous volume compared with the solid from which they came. 

 This sudden expansion causes the breaking and rending of the 

 surrounding material. 



The question which very naturally arises is : Why does the 

 powder burn when there is apparently no air, or oxygen, 

 present ? We have learned that oxygen must be present in 

 other cases of combustion, and this example is no exception. 

 The chemicals of which the powder is made contain the oxy- 

 gen in just the right proportion to produce complete combus- 

 tion, and it is so thoroughly blended that the combustion takes 

 place throughout the whole mass at the same time. This 

 kind of combustion is called deflagration. The smoke of 

 powder is not carbon, but is due to the formation of a small 

 amount of solid matter. Where no solid matter is formed, 

 we have smokeless powder. 



References : 



1. 1703 : 30. Deflagration. 



a. 1704 : 307-308. Gunpowder. 



b. 1705 : 180. Nitroglycerine and Guncotton. 



c. 1707 : 331-333. Gunpowder. 

 Also see references under Section 1. 



8. GAS AND GASOLINE ENGINES 



Blasting is only one of the uses we make of explosions. If 

 the explosions are limited, or controlled, and one part of the 



