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Page 16
Powder 1
Dynamite No. 2, containing 50 per cent. nitro-glycerine 3
For open blasting:
Dynamite No. 3, containing 30 per cent. N.G. 1.0
Dynamite No. 1, containing 75 per cent. N.G. 2.5
Blasting gelatine 3.5
For tunneling:
Dynamite No. 3, containing 30 per cent. N.G. 1
Dynamite No. 1, containing 75 per cent. N.G. 3
Explosive gelatine 19
Finally Berthelot's theoretical calculations give a specific pressure
of--
Powder 1
Dynamite 13
Gun-cotton 14
Nitro-glycerine 16
Blasting gelatine 17
It will be observed that the practical results vary largely from the
theoretical values, but they seem to indicate that gun-cotton and No.
1 dynamite are very nearly equal to each other, and that in the
nitro-glycerine compounds, except where gun-cotton is added, the force
appears to be nearly in proportion to the nitro-glycerine contained.
From the foregoing it seems fair to estimate roughly the values of
bursting charges of shells as follows:
Powder 1
Gun-cotton and dynamite 6 to 10
Nitro-glycerine 13 to 15
Blasting gelatine 15 to 17
Attention has been turned in Europe for more than thirty years toward
firing high explosives in shells; but it is only within very late
years that results have been reached which are claimed as
satisfactory, and it is exceedingly difficult to obtain reliable
accounts even of these. Dynamite was fired in Sweden in 1867 in small
quantities, and a few years later it was fired in France. But two
difficulties soon presented themselves. If the quantity of
nitro-glycerine in dynamite was small, it could be fired in ordinary
shells, but the effect was no better than with gunpowder. If the
dynamite was stronger in nitro-glycerine, it took but a small quantity
to burst the gun.
As early as 1864, dry gun-cotton was safely fired in shells in small
quantities, but when a sufficient quantity to fill the shell cavity
was used, the gun burst. Some few years ago it was found that if the
gun-cotton was either wet or soaked in paraffin, it could be fired
with safety from powder guns in ordinary shells, provided the quantity
was small in proportion to the total weight of the shell--say five or
six per cent. But a new difficulty arises from the fact that it breaks
the shell up into very small pieces, and it is an unsettled question
among artillerists whether more damage is done to an enemy by breaking
a shell into comparatively large pieces and dispersing them a long
distance with a bursting charge of powder, which has a propulsive
force, or by breaking it with a detonating compound into fine pieces,
which are not driven nearly so far. When used against troops there is
also the objection to the high explosive shell that it makes scarcely
any smoke in bursting, and smoke at this point is useful to the
artillerist in rectifying his aim.
In the matter of shells for piercing armor, however, there are no two
opinions regarding the nature of the bursting charge. To pierce modern
armor at all a shell must be made of forged steel, so thick that the
capacity of the cavity for the bursting charge is reduced to
one-fourth or one-fifth of what it is in the common shell; the result
is that a charge of powder is frequently not powerful enough to burst
the shell at all; it simply blows the plug out of the filling hole in
the rear. In addition it is found that in passing through armor, the
heat generated is so great that the powder is prematurely ignited.
If then we can fill the small cavity in the shell with an explosive
which will not ignite prematurely, and yet will burst the shell
properly after it has passed through the armor, the problem will be
solved. Wet or paraffined gun-cotton can be made sluggish enough to
satisfy the first condition; but at present the difficulty is to make
it explode at all. The more sluggish the gun-cotton, the more powerful
must be the fuse exploders to detonate it, and such exploders are
themselves liable to premature ignition in passing through the armor.
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