AGE OF THE EARTH AS AN ABODE FITTED FOR LIFE. 349 



quickly it would cool wlieu wholly solidified, take a large macadamizing 

 stone and heat it red-hot in an ordinary coal fire. Take it out with a 

 pair of tongs and leave it on the hearth or on a stone slab at a distance 

 from the fire, and you will see that in a minute or two, or perhaps in 

 less than a minute, it cools to below red heat. 



27. Half an hour ' after solidification reached up to the surface in 

 any part of the earth the mother liquor among the granules must have 

 frozen to a depth of several centimeters below the surface, and must 

 have cemented together the granules and crystals, and so formed a 

 crust of primeval granite comparatively cool at its upper surface and 

 red-hot to white-hot, but still all solid a little distance down, becoming 

 thicker and thicker very rapidly at first, and after a few weeks certainly 

 cold enough at its outer surface to be touched by the hand. 



PKOBABLE OKIGIN OF BASALTIC ROCK. 



28. We have hitherto left without much consideration the mother 

 liquor among the crystalline granules at all depths below the bottom 

 of our shoaling lava ocean. It was probably this interstitial mother 

 liquor that was destined to form the basaltic rock of future geological 

 time. Whatever be the shapes and sizes of the solid granules when 

 first falling to the bottom, they must have lain in loose heaps with a 

 somewhat large proportion of space occupied by liquid among them; 

 but at considerable distances down in the heap the weight of the super- 

 incumbent granules must tend to crush corners and edges into fine 

 powder. If the snow shower had taken place in air, we may feel pretty 

 sure, even with the slight knowledge which we have of the hardnesses of 

 the crystals of feldsi)ar, mica, and hornblende, and of the solid granules 

 of quartz, that at a depth of 10 kilometers enough of matter from the 

 corners and edges of the granules of different kinds would have been 

 crushed into powder of various degrees of fineness to leave an exceed- 

 ingly small proportionate volume of air in the interstices between the 

 solid fragments. But in reality the effective weight of each solid par- 

 ticle, buoyed as it was by hydrostatic pressure of a liquid less dense 

 than itself by not more than 20 or 15 or 10 per cent, can not have been 

 more than from about one-fifth to one-tenth of its weight in air, and 

 therefore the same degree of crushing effect as would have been expe- 

 rienced at 10 kilometers with air in the interstices, must have been 

 experienced only at depths of from 50 to 100 kilometers below the bot- 

 tom of the lava ocean. 



29. A result of this tremendous crushing together of the solid gran- 

 ules mast have been to press out the liquid from among them, as water 

 from a sponge, and cause it to pass upward through the less and less 

 closely packed heaps of solid particles and out into the lava ocean 



1 Witness the rapid cooling of lava running red-hot or white-hot from a volcano, 

 and after a few days or weeks presenting a black, hard crust, strong enough and cool 

 enough to be walked over with impunity. 



