Geology and Natural History. 221 
small, as we may please to view it) from the interior of our globe 
disposed of ? 
What does it do in the interior? We have already seen that it 
of diminishing the earth’s volume as a whole, and in so doing 
crushing portions of the solid surrounding shell. 
tom, 
a cartload of granite paving-stones shot out in the dark, we see 
by their collision; if we rub two pieces of 
Place by the crushing of the rocky masses of our cooling and de- 
vastly greater scale. It is in this local transformation of work 
© 
ask the qu ion, How nd to answer this, we must deter- 
he experimentally how much heat can be developed by the 
erushi iven v e, say a cubic mile, of such rocky ma- 
terials as we k must constitute the crust of our globe down to 
the bottom of the k sedimentary strata, and extending to 
such crystalloid rocks as w: ay presume underlie these 
Must also obtain, at least approximately, what are the co-efficients 
€ first I have determined experimentally by two different 
methods, but principally b nd 
in crushing prisms i 
s 
och | 
: 772 ‘ + 
'S the heat corresponding to the work expended in the cate 
€xpressed in British units of heat. The following were t 
xperimented upon: Caen stone, Portland (both oolites), magne- 
* 
