THE HISTORY OF EXPLOSIVE AGENTS. 
493 
moment by the layer of water acts as effectually in intensifying the force of explosion, 
as a thin sheet metal case does with the mercuric fulminate, or as a strong iron shell 
with gun-cotton or gunpowder. 
The product of the action of nitric acid upon glycerine, which is known as nitrogly- 
cerine or glonoine, and which, as regards its power of sudden explosion, bears some 
resemblance to the chloride and iodide of nitrogen, appears to be susceptible of only 
two varieties of decomposition. If a sufficient source of heat be applied to some portion 
of a mass of this liquid in open air, it will inflame and burn gradually without any 
explosive effect ; and even when nitroglycerine is confined, the development of its explo- 
sive force by the simple application of flame or of other sources of heat, by the ordinary 
modes of operation, is difficult and very uncertain. But if the substance be submitted 
to a sudden concussion, such as is produced by a smart though not very violent blow 
from a hammer upon some rigid surface on which the nitroglycerine rests, the latter 
explodes with a sharp detonation, just as is the case with gun-cotton. Only that portion 
of the explosive agent detonates which is immediately between the two surfaces brought 
into sudden collision ; the confinement of this portion between the hammer and the 
support, combined with the instantaneous decomposition of the portion struck, prevent 
any surrounding freely exposed portions from being similarly exploded by the detonation. 
A similar result is obtained if any explosive compound or mixture be submitted to a 
sufficiently sharp and violent blow, but the tendency of surrounding particles to become 
inflamed by the detonation is in direct proportion to the rapidity of explosive action of 
the substances. 
The practical difficulties and uncertainty which attend attempts to develope the explo- 
sive force of nitroglycerine by the agency of flame or the simple application of any 
highly heated body, even when the material is confined in strong receptacles (such as 
iron shells or firmly tamped blast-holes), appeared fatal to any useful application of the 
powerful explosive properties of this substance, until M. Alfked Nobel’s persevering 
labours to utilize nitroglycerine, eventually resulted in the discovery of a method by 
which the explosive power of the liquid could be developed with tolerable certainty. 
M. Nobel first employed gunpowder as a vehicle for the application of nitroglycerine. 
By impregnating the grains of gunpowder with that liquid, he added considerably to the 
destructive force of the powder when exploded in the usual way, in closed receptacles. 
M. Nobel’s subsequent endeavours to apply nitroglycerine per se were based upon the 
belief that its explosion might be effected by raising some portion of a quantity of the 
liquid to the temperature necessary for its violent decomposition, whereupon an initiative 
explosion would be produced which w r ould determine the explosion of any quantity of 
the substance. 
I have never succeeded in effecting the explosion of nitroglycerine by simply bringing 
it into contact with an inflamed or incandescent body, but the following results illustrate 
the manner in which a source of heat may operate in accomplishing the explosion of 
this substance. 
