156 Nitro-Glycerine : [ April, 
and can be removed by means of a siphon, or, by simply pouring it 
off. The blasting liquid is now ready for use. It would seem that 
the methyl-alcohol is by this means separated very readily from the 
nitro-glycerine held in solution by it. If protected blasting liquid 
be kept in a closed vessel, it will remain in that state for an in- 
definite period of time, and ready at any moment to be reduced 
or rendered fit for action; if, however, it be exposed in an open 
vessel it will regain its explosiveness, in periods of time propor- 
tionate to the amount or degree of exposure. In the experiments, 
for instance, which were instituted by the Prussian Military Com- 
mission, it was observed that protected nitro-glycerine, exposed to 
the air in an open glass, only acquired explosiveness on the twenty- 
first day, although it was tried every second or third day; and 
such protected liquid, after being exposed in an open bottle with 
a narrow neck for twenty-one days, exhibited no tendency to ex- 
plosion even then,—thus showing that comparative confinement of 
the liquid very greatly retards the evaporation of the solvent and 
protecting wood-spirit. 
As an explosive capable of being practically used, nitro-glycerine 
is quite an exceptional substance, from the circumstance of its being 
a liquid compound. There are other liquid explosives,—as the 
so-called chloride of nitrogen, for instance,—but nobody has ever 
yet succeeded in practically applying them, or even ventured to 
prepare any of them in large quantity. The force exerted by nitro- 
glycerine, during an explosion, is truly marvellous; indeed, no 
correct conception can be formed of it by any person who has not 
himself experimented with it, or has, at all events, seen the experi- 
ments performed. Weight for weight the new explosive is ten times 
more powerful than gunpowder. ‘The extraordinary mechanical 
or eruptive power which it exerts is partly owing to the fact that 
there is no solid residue attending the explosion, and that the 
enormous pressure exerted by the resulting gases is due to the 
great rapidity of the explosion. The rocks being blasted have not 
time enough permitted them to effect any sensible cooling and con- 
densing of the vapours. In fissured rocks this rapidity of explosion 
is of immense consequence; it is so very great that the tamping 
employed in blasting operations, is in many cases not ejected from 
the bore-holes, although—by preference—it is almost invariably 
quite loose, consisting of sand, slate-dust, or other finely-divided 
solid matter, or even ordinary water. 
Hard tamping is of comparatively little use, owing to another 
very curious property possessed by nitro-glycerine, namely, that of 
“striking down,” as it has been called, or of exerting its explosive 
foree—unlike gunpowder-—almost entirely in a downward direc- 
tion. This circumstance is intimately connected with the explosion 
on board, and ultimate destruction of, the steamship ‘ Huropean’ 
