148 
POPULAR SCIENCE REVIEW. 
even bum when enclosed in ordinary boxes, producing only 
slightly noxious gases and very little or no smoke. It ex- 
plodes only in completely closed spaces, and with difficulty 
b^ means of sparks. It may be, when thus confined, exploded 
by glowing hot metals, by bullets fired into it, and otherwise by 
deliberate artificial ignition. The disadvantage urged against 
it in its practical application is that when the temperature 
falls below 6° Centigrade, it hardens, and that then, par- 
ticularly when loose cartridges or a series of cartridges are 
employed, the whole of the charge is not exploded, but a 
portion remains altogether undamaged, or is blown out un- 
exploded. The cause of this stiffening is of course due to the 
natural crystallisation of the nitro-glycerine. 
Lithofracteur, the invention of Professor Engels, is an im- 
provement upon dynamite, and derives its advantages from the 
diminution of the proportion of siliceous meal as well as of 
the nitro-glycerine, the balance being made good by other 
ingredients of an explosive nature, the details of which con- 
stitute the secret of its manufacture, for neither abroad nor in 
this country has it yet been patented, Messrs. Krebs, of Cologne, 
the manufacturers, preferring reticence in this respect to the 
publicity which patents would necessarily give. It had acquired 
some time ago considerable reputation in Prussia, but became 
known in England through the military operations in which it 
was employed during the late Franco-Prussian war. It also is 
produced in a plastic state, being black in colour and doughy 
in consistency. When lit by a match or a cigar, like dynamite, 
it merely burns ; but it is almost insensible to blows or 
pressure, and can only be exploded by a strong priming cap or 
detonator composed of the strongest fulminate. Attempts to 
explode it by charges of gunpowder have failed. How little 
sensitive it is to violent shocks has been shown by throwing it 
over cliffs of 150 ft. or 200 ft. in height; as also by firing shells 
fitted with it from cannon, which exploded only when they 
reached some hard object of stone or iron. Neither in com- 
bustion nor explosion does it generate smoke like gunpowder ; 
but the gases formed are transparent, and only detectable by 
the smell. They are not pleasant to inhale largely, as head- 
ache would follow ; but as diluted in the open air they cannot 
be regarded as poisonous, although it will be better to avoid 
being too much enveloped in them. 
The advantages of lithofracteur over the old blasting gun- 
powder are very remarkable, and although the latter for certain 
work will still maintain its ground, the former will have pre- 
dominance in a majority of operations. Besides its more 
energetic action and the important savings of time, labour, 
and tools which is effected by its use, its advantages are especially 
