300 ANNUAL EEPOET SMITHSONIAN INSTITUTION, 1910. 



bomb, in a wooden-insulating vessel provided with a wooden cover. 

 The accessories consist of a framework stirring device rotated or 

 raised by an electric motor with which to bring the entire mass of 

 water to a uniform temperature, a thermometer with open scale read- 

 ing to one one-hundredth of a centigrade degree, a magnifying glass 

 with which to read this thermometer, a pair of scales on which to 

 accurately weigh the several parts of the system and the water that 

 is used, a hocking frame to raise the vessels from the scales and 

 deposit them in place, and a machine with which to fire the charge. 



The water equivalent of the calorimeter ha^dng been determined 

 and the effect of the detonator and tin-foil wrapping having been 

 ascertained a charge of 100 grams of the explosive, wrapped in tin 

 foil, is connected with a No. 7 electric detonator and suspended in 

 the bomb, which is closed and exhausted down to 10 millimeters of 

 mercury. The inunersion vessel having received its weighed charge 

 of water all the parts of the calorimeter are assembled and the stir- 

 ring device set in motion to bring the water, and therefore all essen- 

 tial parts of the calorimeter, to a common temperature. When the 

 thermometer immersed in the water shows that a constant tempera- 

 ture has been reached the charge is fired and the rise in temperature 

 recorded on the thermo)neter carefully observed until the mercury 

 has reached its greatest altitude in this experiment. From this data, 

 together with that referred to above, the number of calories given by 

 a known weight of the explosive is found. 



In firing by dentonation it is essential for safety and success in 

 blasting that when the reaction is once initiated by the detonator 

 it shall proceed throughout the column of explosive for otherwise 

 a portion of the charge may be thrown out of the bore hole unex- 

 ploded but inflamed, producing a "blown-out shot" which may 

 ignite the fire damp or coal-dust-air mixture, or a portion may be 

 left in the bore hole unexploded where it constitutes a source of 

 danger in subsequent operations, or it may be brought down mixed 

 with the coal to produce trouble in the breakers, in transportation, 

 or in the use of the coal. The test employed to ascertain the relative 

 sensitiveness of explosives to the detonation of masses of their own 

 kind is called the explosion by influence test. I have applied this 

 term to the testing of explosives for their sensitiveness to the initial 

 detonation of a standard explosive, and described the method in the 

 Journal of the American Chemical Society 15, 10-18 ; 1893. A com- 

 mercial method now used for some time is one in which the cartridges 

 are placed in rows on the ground, or other support, with spaces be- 

 tween each, and varying the intervals^between the cartridges in suc- 

 cessive trials. A more modern and severer test is to so bind two 

 cartridges together with wire that they may be suspended vertically 

 in the air, end to end, at a carefully measured distance apart, a 



