34 « 
Infusorial Earth and its Uses. 
[July, 
moulds. The cartridges are simple cylinders, protected by 
parchment paper. If ordinary paper is used the oil soaks 
into it, and there is great danger of premature explosion. 
Dynamite is a brownish grey, sometimes reddish, inodorous, 
pasty, greasy mass, having the specific gravity of i*6. When 
ignited by an ordinary flame, it burns up quickly without 
detonation, and must therefore be fired with a patent ex- 
ploder containing fulminate of silver inclosed in a copper 
capsule. It requires a heavy blow of a hammer on an anvil 
to explode it, and even then only the portions struck are 
fired. In this respeCt it presents great advantages over 
nitro-glycerine, which is easily exploded by percussion. On 
the other hand, the wood of the boxes in which dynamite is 
packed becomes by slow degrees impregnated with nitro- 
glycerine, and forms a most dangerously explosive material, 
which may give rise to serious accidents in warehouses 
where it is stored. As long as the nitro-glycerine is con- 
fined in the infusorial silica there appears to be very little 
danger, but the escape of a few drops of the oil may be the 
source of great mischief. The force exerted by the dynamite 
is much greater than that of gunpowder, and under the 
name of giant powder it has been largely employed in the 
mines of California. Other explosives, such as dualine and 
lithofraCteur, may be said to be varieties of dynamite, 
having nitro-glycerine for their base, and using saw-dust or 
some other substance as an absorbent. All of them are 
powerful explosives, and must be handled with care. 
For the preparation of cements and of artificial stone a 
number of processes have been devised, in which infusorial 
earth plays a prominent part, viz. : Equal parts of infusorial 
silica and litharge, and one-half part of slaked lime, stirred 
to a paste in linseed oil, is affirmed to become as hard as 
sandstone on setting, and is recommended as an excellent 
compound for cementing stone, metal, and wood. The 
following recipe, again, is pronounced to be serviceable for 
the production of an artificial stone for art objects. For this 
purpose the infusorial earth is intimately mixed with well- 
pulverised, freshly-burned lime, in the proportion of from 
three to six parts of the former to one of the latter. The 
mixture is then pressed into moulds under an addition of a 
very slight quantity of water. The resulting produCt, a 
silicate ol lime, is formed with the evolution of considerable 
heat. The objeCts produced ultimately attain great hard- 
ness ; they are perfectly water-proof, and may readily be 
coloured with any colour used in stereochromy. 
In combination with sulphur, infusorial earth forms a 
