Page:Popular Science Monthly Volume 56.djvu/315

Rh effects, is set in operation by what appears to be a very slight initial cause. It is evident on brief consideration that these bodies, like a coiled spring, a bent bow, or a head of water, are enormous reservoirs of energy which can be released at a touch, and which, if



the explosive be properly placed in well-proportioned amounts and discharged at the right time, can be made to do useful and important work that can not be as conveniently and quickly accomplished in most cases, and in some cases can not be accomplished at all by any other means.

The marked characteristic of all explosive substances, and especially of the so-called high explosives, is that the energy, as developed, is at high potential, and the uses to which energy in this condition can be economically put are so manifold that the production of explosives has become one of the most important of our chemical industries, this country alone producing, in 1890, 108,735,980 pounds, having a value of nearly $11,000,000.

The number of possible substances possessing explosive properties is exceedingly large; the number actually known is so great that it has taxed the ingenuity of inventors to provide them with suitable names; but these various explosive substances vary to so great an extent in the energy they will develop in practice and in their safety in storage, transportation, and use that but a comparatively small number have met with wide acceptance. All may be