ME. EOBEET MALLET ON VOLCANIC ENEEG-Y. 
225 
The specific heat of silicic anhydride, Si0 2 , is given by Watts (Chem. Diet. “Heat,” 
vol. iii. p. 32) as =0-19132, water being unity ; 0-179 by my determination of quartz 
from Wicklow, Ireland. 
Specific beat of quartz 0-1719 (Hermann) i Gmelin’s Handbook, 
0-1913 (Regnault)/ vol. i. p. 245. 
Now the average of the whole data results in these : — 
042 lbs. falling 0-8302 foot 65*5 times per minute for 24 hours, 
Produces 4032 lbs. of quartz in powder, 
116-571 meshes per square inch; 
or 642 lbs. falling 0-8302x65-5 = 54-3781 feet per minute for 24 hours, 
or 24x60=1440 minutes =78304-464 feet. 
That is, 642 lbs. x 78304*464 feet =50,271,465,888 foot-pounds, being the work done 
to crush to powder 4632 lbs. of quartz, 
or 888 = 10853' 08 foot-pounds per 1 lb. of quartz, 
or 10853-08 foot-pounds x 165-431 lbs. = l, 795, 435, 877 foot-pounds per cubic foot 
of quartz of specific gravity 2-6469. 
Then, dividing by Joule’s equivalent, we have 
1795435-877 
2325-69 degrees Fahrenheit in 11b. of water as the equivalent of the 
crushing work per cubic foot of quartz ; or, as steam from water at 32° of 1 atmosphere 
and therefore at 212° contains 1146-7 units of heat, the work of crushing 1 cubic foot of 
quartz would vaporize at 212 degrees 2-028 lbs. of water, for 
2325-69 : 1146-7 
1 gives X- 
2325-69 
1146-7 
r=2-028. 
Now let us take the results, not from general averages, but from the highest and lowest 
data given, having regard to the fineness of the pulverized quartz produced, i. e. assuming 
that the average finest powder is due to the largest expenditure of power. 
Then, first, we have from what precedes, that ( highest ) 860 lbs. falling 1-0951 foot 
78-857 times per minute produces in 24 hours 2528 lbs. of quartz-powder of fineness to 
pass through 167*0 parts of a square inch, 
or 860 lbs. falling 1-0951 x 78-857 = 86-356 feet per minute, 
or 86-356x1440 = 124352-64 feet per day of 24 hours, 
which is 860 lbs. x 124352-64 feet =106943270-4 foot-pounds, being the work done to 
2528 lbs. of quartz, 
or 
106943270-4 
2528 
= 42303-5 foot-pounds expended per 1 lb. of quartz, 
