i:\< AVATIM, MArHlNKS A\l> K" K KK1LL8 



Tamping. - 'ramping is the material placed in the hole above 

 the explosive to prevent the gases of exploMon from escaping 

 into tlie air. Tamping generally consists of clay. When gun- 

 powder is used the clay must be well rammed with a wooden 

 tool, and paper, cotton, or some other dry material must be 

 placed between the moist clay and the powder. When dyna- 

 mite is used it is not necessary to ram the tamping, since the 

 suddenness of the explosion shatters the rock l>efore the clpy 

 can be driven from the hole. 



A few experienced men should be appointed to fire the 

 blasts. These men should give ample warning previous to the 

 blast in order that all machinery and tools which might be 

 injured by flying fragments may be removed out of danger, and 

 so that the workmen may seek safety. When all is ready they 

 should fire the blasts, keeping accurate count of the explosions 

 to ensure that no holes have missed fire, and should call the 

 workmen back when all danger is over. In case any hole has 

 missed fire it should be marked by a red lamp or flag. 



Nature of Explosions. When the explosives are ignited a 

 sudden development of gases results, producing a sudden ami 

 violent increase of pressure, usually accompanied by a loud 

 report. The energy of the explosion is exerted in all directions 

 in the form of a sphere having its center at the point of explo- 

 sion, and the waves of energy lose their force as the distance 

 frmii this central point increases. The energy of the explosion 

 at any point in the sphere of energy is, therefore, inversely 

 proportional to the distance of this point from the center of 

 explosion. In the vicinity of the center of explosion the gaaea 

 have sufficient power to destroy the force of cohesion and 

 shatter the rock ; further on, as they lose strength, they only 

 destroy the elasticity of the material and produce cracks; and 

 still further away they only produce a shock, and do not affect 

 the material. Within the sphere of energy there are, therefore, 

 three other concentric spheres: the first one being where 

 cohesion is destroyed, the second where elasticity if overcome, 



