ME. EOBEET MALLET ON VOLCANIC ENEEGY. 
191 
( 4 ) 
6472 
62 425 x 1146 
= 0 - 0904 = cubic feet of water at 
32° evaporated into steam at 212° ; 
or if the water be already at 212°, 
6472 
64.405 x 966 = 0‘107 cubic feet evaporated into steam of 1 atmosphere. 
6472 
(5) x q.i 99 =183°'74 — degrees of temperature by which 1 cubic foot of mean rock 
is raised by H. 
Taking 2000° Fahr. as the fusing temperature of such rock, 
6472 
(6) .)( 3i 3 0 ~ x [ — x Q. 1C j9 = 0'0918 = the number of cubic feet of mean rock at zero fused 
by II. 
If the rock be previously at 300° Fahr., then 
6742 
, 77. =0T08 = the cubic feet of rock so fused : 
1/00x 1/7x0-199 ’ 
and if the rock at 300° be only heated to 1000° Fahr., or to a bright red heat (the 
melting-point of silver), 
6472 
— 7T T 677=0-2G2=the cubic feet of rock so heated by H. 
700 x 177 x 0-199 J 
134. From (3) it follows that the heat of liquefaction of 1 cubic mile of ice at 32° melted 
is equivalent to the crushing work of 1*277 cubic mile of mean rock when transformed 
into heat. 
135. We have now to describe the second series of experiments, viz. those for the 
determination of the total amount of contraction of mineral masses analogous to those 
which we may suppose constitute the solid shell and probably the greater portion of our 
globe, upon cooling from their temperatures of fusion, or above that by known amounts, 
down to that of the mean of our atmosphere. 
The experiments or observations that have heretofore been made on the subject are 
of the most unsatisfactory character, and contain such elements of error as to be wholly 
unreliable. 
Bischoff’s experiments on the total contraction of fused basalt, trachyte, and granite, 
&c. (originally recorded in Leonhard and Bronx’s ‘ Neues Jahrbuch fiir Mineralogie &c.,’ 
vol. for 1841, p. 565 &c., and vol. for 1843, pp. 1-54, the last containing the details of 
experiments by Bisciioff himself) have been accepted merely on authority, and quoted 
by authors in book after book apparently without the details of the methods of expe- 
riment having been consulted in the original memoirs. Thus Professor W. Thomson 
(Thomson and Tate, Nat. Phil. p. 725) says, “Bisciioff’s experiments, upon the validity 
of which, so far as I am aware, no doubt has ever been thrown, show that melted granite, 
slate, and trachyte all contract by something like 20 per cent, by freezing,” and proceeds 
to base on this erroneous coefficient a probable cause for volcanoes and earthquakes 
(pp. 725-727). 
