while ranking among the most violent of explosives, possesses a 
degree of safety which obtains with no other. 
The advantage which accrues from the use of the mercury ful¬ 
minate detonator is two-fold, for it not only enables us to explode 
gun-cotton while the latter is yet too wet to burn, but it also 
causes the gun-cotton to develop a greater force than it manifests 
when exploded bv simple ignition, and, further, it causes the vio¬ 
lent explosion of the gun-cotton when the latter is uncontined. 
It is now a well known fact that when compressed gun-cotton, 
dynamite or other high explosives are freely exposed upon a 
metal plate and detonated, if the plate is sufficiently strong to re¬ 
sist rupture, the explosive leaves a marked and permanent im¬ 
pression upon the plate, the intensity of the impression being, of 
course, dependent upon the intensity and amount of the explosive 
used. This is not surprising when we recall that Berthelot found 
that gun-cotton having a density of i.i developed, when in 
contact, a local pressure of 24,000 atmospheres or 160 tons on 
the square inch, and if we remember too that this enormous pres¬ 
sure is realized in an exceedingly brief space of time. The effect 
may, of course, be enhanced if the explosive be tamped with 
earth, water and the like, but as Cooke* has so clearly shown, in 
his essay on the “ Atmosphere as an anvil,” the aerial fluid 
may serve as a tamp just as the aqueous one does, though not as 
efficiently 
It is perhaps not so well known a fact that the impression pro¬ 
duced by the exploding mass is an almost exact copy of the form 
of that surface of tlie explosive which was in contact with the 
plate of metal. This feature is best observed with compressed 
gun-cotton, since, as it is a papicr-machc like body, it is possible 
to shape it as we lancv, and to stamp upon its surface such figures 
and designs as we wish. 
The lirst recorded observation of this phenomena of which I 
am aware, is that made by Lieutenant Max von Forster of VVals- 
rode.f lie savs. that when a piece of compressed gun-cotton is 
detonated on a plate of iron, an accurate impression of the form 
of the under surface of the gun-cotton is produced, every angle, 
every projection and every indentation present in the gun-cotton 
•Popular Science Monthly, 5, jao; 1S74. 
TVan Xostnunl'a Eng. Mag., 31, 113; Aug., 1SS4. 
