per cent. of naphthalene in
nitro-glycerine, 3 parts of chalk, 7 parts of sulphate of barium, and 20
of kieselguhr.

Kieselguhr dynamites are being largely given up in favour of gelatine
explosives. The late Colonel Cundill, in his "Dictionary of Explosives,"
gives a list of about 125 kinds of dynamites. Many of these, however, are
not manufactured. Among the best known after the ordinary No. 1 dynamite
are forcite, ammonia dynamite, litho-fracteur, rendock, Atlas powder,
giant powder, and the various explosive gelatines. They all contain nitro-
glycerine, mixed with a variety of other substances, such as absorbent
earths, wood-pulp, nitro-cotton, carbon in some form or other, nitro-
benzol, paraffin, sulphur, nitrates, or chlorates, &c. &c.

~Blasting Gelatine and Gelatine Dynamite.~--The gelatine explosives
chiefly in use are known under the names of blasting gelatine, gelatine
dynamite, and gelignite. They all consist of the variety of nitro-
cellulose known as collodion-cotton, i.e., a mixture of the penta- and
tetra-nitrates dissolved in nitro-glycerine, and made up with various
proportions of wood-pulp, and some nitrate, or other material of a similar
nature. As the gun-cotton contains too little oxygen for complete
combustion, and the nitro-glycerine an excess, a mixture of the two
substances is very beneficial.

Blasting gelatine consists of collodion-cotton and nitro-glycerine without
any other substance, and was patented by Mr Alfred Nobel in 1875. It is a
clear, semi-transparent, jelly-like substance, of a specific gravity of
1.5 to 1.55, slightly elastic, resembling indiarubber, and generally
consists of 92 per cent. to 93 per cent. of nitro-glycerine, and 7 to 8
per cent. of nitro-cotton. The cotton from which it is made should be of
good quality. The following is the analysis of a sample of nitro-cellulose
which made very good gelatine:-

Soluble cotton 99.118 per cent.
Gun-cotton 0.642 "
Non-nitrated cotton 0.240 "
Nitrogen 11.64 "
Total ash 0.25 "

The soluble cotton, which is a mixture of the tetra- and penta-nitrates,
is soluble in ether-alcohol, and also in nitro-glycerine, and many other
solvents, whereas the hexa-nitrate (gun-cotton),
C_{12}H_{14}O_{4}(ONO_{2})_{6}, is not soluble in the above liquids,
although it is soluble in acetone or acetic ether. It is very essential,
therefore, that the nitro-cotton used i