y the sudden explosion of
dynamite is the same as its heat of combustion,[A] and proportionate to
the weight of nitro-glycerine contained in the mixture. The gases formed
are carbonic acid, water, nitrogen, and oxygen.

[Footnote A: Berthelot, "Explosives and their Power."]

The "explosive wave" (of Berthelot) for dynamite is about 5,000 metres per
second. At this rate the explosion of a cartridge a foot long would only
occupy 1/24000 part of a second, while a ton of dynamite cartridges about
7/8 diameter, laid end to end, and measuring one mile in length, would be
exploded in one-quarter of a second by detonating a cartridge at either
end.[A] Mr C. Napier Hake, F.I.C., the Inspector of Explosives for the
Victorian Government, in his paper, "Notes on Explosives," says: "The
theoretical efficiency of an explosive cannot in practice be realised in
useful work for several reasons, as for instance in blasting rock--

"1. Incomplete combustion.

"2. Compression and chemical changes induced in surrounding material.

"3. Energy expended in cracking and heating of the material which is not
displaced.

"4. The escape of gas through the blast-hole and the fissures caused by
the explosion.

"The useful work consists partly in displacing the shattered masses. The
proportion of useful work obtainable has been variously estimated at from
14 to 33 per cent. of the theoretical maximum potential."

[Footnote A: C.N. Hake, "Notes on Explosives," _Jour. Soc. Chem. Ind._,
1889.]

Among the various forms of dynamite that are manufactured is carbo-
dynamite, the invention of Messrs Walter F. Reid and W.D. Borland. The
base is nitro-glycerine, and the absorbent is carbon in the form of burnt
cork. It is as cheap as ordinary dynamite, and has greater explosive
force, seeing that 90 per cent. of the mixture is pure nitro-glycerine,
and the absorbent itself is highly combustible. It is also claimed that if
this dynamite becomes wet, no exudation takes place.

Atlas powder is a dynamite, chiefly manufactured in America at the Repanno
Chemical Works, Philadelphia. It is a composition of nitro-glycerine,
wood-pulp, nitrate of soda, and carbonate of magnesia. This was the
explosive used in the outrages committed in London, by the so-called
"dynamiters." Different varieties contain from 20 to 75 per cent. of
nitro-glycerine.

The Rhenish dynamite, considerably used in the mines of Cornwall, is
composed of 70 parts of a solution of 2 to 3