208 
MR. ROBERT MALLET ON VOLCANIC ENERG-Y. 
melting-point of silver) and the fused material to 2000° Fahr. (that of liquid cast iron) 
from the initial temperature. 
188. It follows from equation (6) that 1 cubic mile of crushed mean rock will thus 
heat 0-262 cubic mile of the heated material, or will fuse 0T08 cubic mile of the fused 
material, the specific heat of all being taken as the same. 
And from the relative proportions of the dust and scorise to lava above assigned, 
we obtain as the result that 1 cubic mile of crushed mean rock will supply the quantity 
of heat necessary for 0-255 cubic mile of the mixed heated and fused material consti- 
tuting a volcanic cone, or that 3-92 cubic miles of crushed mean rock is required for 
each cubic mile of volcanic cone. 
Hence each such cone of the volume previously assigned requires 6'54x 3-92 = 15-636 
cubic miles of crushed mean rock for its heating work. 
We have to add to this the lifting work as previously found =0-888 cubic mile, in 
total =16-524 cubic miles of crushed rock. 
189. We have further to estimate the waste. From the low average conductivity of 
rock materials (perhaps not that of silver) the loss of heat by conduction to the walls 
of the volcanic focus and tubes to surface may be taken as insensible. The main source 
of waste is in heat units expended in producing steam, that yields no effective action in 
lifting or is spent in aerial ejection above the crater. 
190. We have no data for more than a probable conjecture as to what may be the 
average amount of this. It may be remarked, however, that the sources of loss of effective 
action of the steam here do not resemble those in the steam-engine, in which, as Hirn 
has shown, about nine units of heat are wasted to one utilized, but rather resemble 
those of the gunpowder-gases in a cannon through windage and powder blown out 
unconsumed, See., the losses from which ballistic experiments prove to be much smaller. 
We shall allow, therefore, here that double the units of heat utilized in lifting 
are wasted, or that three times the lifting work is that actually expended, or 
3x0-888 = 2-664 cubic miles of crushed mean rock. 
191. Thus the lifting, heating, or fusing, and wasted work together, for one volcanic 
cone of the mean volume above assigned, demand a total of 18-3 cubic miles of crushed 
mean rock, or 18 cubic miles in round numbers. 
192. Now there are about 400 volcanic cones known or stated to exist on the globe (a 
number sanctioned by FIumboldt and other good authorities), and averaging them all at 
the dimensions above, we find that 400x18 = 7200 cubic miles of crushed rock w T ould 
have sufficed for their production. 
193. [It thus appears that were the entire of the 987 cubic miles of crushed rock 
representing the annual loss of heat of our globe all consumed in volcanic energy, it 
would suffice to form all the volcanic cones upon our earth in less than eight years. 
Tens of thousands of years have been actually spent on the operation, from which 
we may see how excessively small must be the amount annually expended in vulca- 
nicity.] 
