Geology and Natural History. 147 
British heat-units per cub. foot of rock crushed, pt BAS 
Temperature Fahr. to which it is raised,...--.-------- =183°74 
Cub. foot of rock at 300° F., fusible at 3,000° by crush- 
ig J. cub,.foot of. mean rock,....u fine. necauec anes = 0:108 
Passing t 
eral masses, Mallet shows the unreliability of the experiments 
3,000°. The slag cones were again measured, after cooling, at 53° 
Mean coéfticient of contraction from fluidity to solidification, 
3680° to 3000° F. = 6°982° 
3680° to 538° 0°932°76 
which is about 6 per cent, against 20-25, as determined by 
Bischof. 
usually given we adopt, the annual loss cannot be less than 575 
amount annually lost were produced by rock-crushing, it would take 
987 cubic miles of crushed rock. But doubtless by far the greater 
part reaches the surface from a cooling nucleus, and but a small 
portion is manifested as vulcanicity. Upon an estimate of the 
entire mass of volcanic cones known, Mallet comes to the conclu- 
sion that 7,200 cubic miles of crushed rock would have sufficed 
ela sed during their production is immense. : 2 
aving proved that the crushing of the earth’s solid crust 
affords a supply of energy sufficient to account for terrestrial vul- 
8 a - 
the crust to contraction will naturally be, not continuous, but per 
