THE LITHOFEACTEUE. 
147 
THE LITHOFEACTEUE. 
By S. J. MACKIE, F.G.S. 
[PLATE LXXXIII.] 
I T is not a little remarkable that the compounds of nitro- 
glycerine — a substance so mercilessly decried in this 
country for years past — should now have come to the front as 
the safest as well as the most powerful of explosives. Nitro- 
glycerine, or nitrate of glycerine, was discovered in the year 1847 
by the Italian chemist Sombrero. It is a pale yellow oily 
fluid, of 1*6 specific gravity, which commences to stiffen and 
solidify when the temperature falls below 8° Centigrade, 
or 47° of Fahrenheit. It is insoluble in water, but can be 
mixed with methylated spirit, benzole, nitro-benzole, or a mix- 
ture of alcohol and ether. Against the use of pure nitro- 
glycerine a strong prejudice still exists in consequence partly 
of the poisonous nature of the substance, but mainly on account 
of its violent and sensitive nature and the many accidents 
which happened in its earlier applications. The bad character 
given to it by the Newcastle and Caernarvon explosions, how- 
ever undeserved it may have been (for the treatment it was 
subjected to was such as gunpowder itself might have rebelled 
against), has undoubtedly retarded not only its own progress, 
but that of all blasting substances into which it entered 
as a base. Nobel, the Swedish chemist, was the first to tame 
its violence and to put it under complete control, so far as 
safety was concerned, by mixing it with the fine infusorial 
earth so well known to microscopists, and thus forming a 
simple mechanically plastic substance, handier as well as safer 
for use for mining and quarrying purposes. This substance, 
consisting of 75 per cent, of nitro-glycerine and 25 per cent, of 
siliceous meal, was proved both as to safety and power by 
numerous most important and convincing experiments, and has 
attained to a large sale for blasting operations under the name 
of dynamite. Thus compounded, the plastic mass is of a 
tawny reddish hue, of a consistency approaching that of putty. 
Set fire to in the open air, dynamite merely deflagrates ; it will 
