182 
ME, EOBEET MALLET ON VOLCANIC ENEEGY. 
of the work consumed in the crushing of a solid mass of hard rock to powder, is almost 
infinitesimally small. 
101. We may therefore admit that, subject to the inevitable errors of experiment, the 
whole of the work consumed in crushing matter like rocks reappears as heat, or that in 
an experimental cube of the rock crushed to powder by a Aveight W, in pounds, descending 
from a height h, in feet, 
is the number of units of heat developed, J being Joule’s equivalent. 
[The volume and weight of the cube crushed being known, we can deduce the Avork 
required to crush a unit in weight (1 pound) and in volume (1 cubic foot) of each rock 
thus experimented on. 
102. If, then, 
(1) — j^=H=the units of heat produced by the Avork of crushing 1 cubic foot of rock 
(AA 7 hich, assuming the specific heat of Avater constant with respect to temperature, 
represents the number of degrees Fahr. in a pound of Avater, or the number of pounds 
of Avater raised 1 degree by the work of crushing), the weight of 1 cubic foot of Avater at 
point of maximum density being 62-425 lbs., and that of ice 57‘8 pounds, 
(2) 59^05 =T= the temperature to which 1 cubic foot of AA T ater is raised by H ; 
and, taking the heat of liquefaction of ice as 143° Fahr., 
(3) 5^-3^ i 4 3 ~^ e nu mber of cubic feet of ice at 32° melted to Avater at 32° by H. 
Also, the total heat of steam of 1 atmosphere being 114G°=:96G c, + 180 o , 
H 
(4) £ 0-405 x ii 4 g — the number of cubic feet of water at 32° evaporated into steam 
at 212°; also 
(5) g2-4 ofx I60 ~^ ie num ^ er °f cubic feet of Avater at 32° raised to the boiling-point. 
Further, if w be the weight in pounds per cubic foot, and s be the specific heat, 
(G) — = £=the temperature or number of degrees of heat by Avhich 1 cubic foot of 
such rock is raised by H ; 
so that, if / 7 be the temperature of fusion of any rock, 
H t 
(7) =the number of cubic feet of rock capable of being melted from tempe- 
rature 0 by II, 
assuming that the specific heat of the rock is constant as respects temperature, and neg- 
lecting (as small and unknown) its heat of liquefaction"*.] 
[* This passage and the last two columns of_Table I. are modified from what was originally presented to 
the Society.] 
