explosion, of thirteen volumes of carbonic oxide, five parts of watery
vapor, and three of nitrogen, or twenty-one volumes of gas in place of
fifteen. As the power of an explosive depends principally on the amount
of gas which results from its sudden combustion, it was evident that the
addition of pure or nearly pure carbon, in a condition to be readily
combined with the other elements, ought to increase materially the force
of nitro-glycerine, and M. Roca experimented accordingly with an
admixture of sugar, as a highly carbonized body immediately available,
and found that three parts of this, mixed with seven parts of
nitro-glycerine, detonated with a force from thirty to thirty-five per
cent. greater than that of pure nitro-glycerine. Many other organic
carbonaceous substances may be employed in place of sugar, with various
advantages. In comparing these simple compounds with the celebrated
explosive gum, prepared by dissolving gun-cotton in nitro-glycerine, it
is found that the latter is far inferior, having an energy very little
superior to that of pure nitro-glycerine.

* * * * *




THE CIRCLE-DIVIDER.


This little apparatus, invented by Prof. Mora, of Senlis, permits of
dividing circumferences or circles into equal or proportional parts. It
consists (Fig. 2) of a rule, A, divided into equal or proportional parts,
which pivots in the manner of a compass around a rod, T, that serves as a
central rotary point. Along this rule moves a slide, R, provided with an