7 So THE POPULAR SCIENCE MONTHLY. 



mixture is called dynamite, or giant-powder ; it is made by mixing 

 nitro-glycerine with a siliceous earth, in the proportion of three to one 

 by weight. This earth is a fine white powder, composed of the skele- 

 tons of microscopic animals ; it is found in Hanover and also in New 

 Hampshire that coming from the latter locality being the finer, and 

 therefore most used in this country. The dynamite formed by this 

 mixture is not unlike moist brown sugar in appearance ; care must be 

 taken not to put too much nitro-glycerine in it, as there must not be 

 such a quantity as would cause exudation. Its properties as an explo- 

 sive, are, of course, those of the nitro-glycerine alone ; but it can be 

 much more readily handled, and there is less danger from either per- 

 cussion or friction. It has been dropped from a height upon rocks, 

 heavy weights have been allowed to fall upon it, and other experi- 

 ments of a like nature have been made to show how readily it can 

 bear transportation and hard knocks. This safety, however, presup- 

 poses a pure nitro-glycerine ; and whenever an accident occurs it may 

 safely be laid to the impurity of the explosive, and not to anything 

 necessarily consequent upon the use of dynamite. Under the action 

 of cold, dynamite freezes at 40 Fahr. in a hard, compact mass, in which 

 condition it is very difficult to explode. Sometimes, however, it freezes 

 in a loose and powdery state, and there is then no difficulty in causing 

 its explosion with the ordinary fulminate-fuse. Generally speaking, 

 however, it is best with this, as with nitro-glycerine, to thaw it out 

 before attempting to use it. Instances have been known of careless 

 men attempting to do this with a red-hot poker, with consequences, 

 naturally, of a disastrous character. It will admit of being slightly 

 moistened without injury, and hence can be used when gunpowder 

 could not be. As a military explosive for mines and torpedoes, as 

 also for the breaking up and destruction of guns, it has proved itself 

 useful ; and it has been used as a bursting-charge for shells, though 

 this is considered dangerous. 



Besides dynamite, there are several other mixtures of nitro-glycer- 

 ine, in which the inactive siliceous earth is replaced by some active 

 substance, such as charcoal, saw-dust, wood-fiber treated with acid, 

 chlorate of potash, or even gunpowder. It is extremely doubtful 

 whether anything is added to the explosive effect of the nitro-glycerine 

 by their presence, as its own explosion is so rapid as to gain nothing 

 from the slower combustion of these substances. Experiments with 

 the pressure-gauge tend to show the correctness of this theory. Of all 

 these combinations, that called cellulose dynamite is the best ; it is a 

 combination of the wood-pulp, so much used for the manufacture of 

 paper, treated with nitric acid and nitro-glycerine ; it possesses the 

 excellent quality of being able to absorb a considerable quantity of 

 water without injury ; for this reason it may prove itself a commercial 

 rival to dynamite pure and simple. 



Large quantities of dynamite are manufactured in this country for 



