THE PRE-ARCH^AN WORLD. 
19 
iron and form a thin crust on top. As the cooling 
progresses this becomes thicker, and begins to wrinkle, 
forming mountains much greater in proportion than 
those of the earth. Soon signs of volcanic action 
may be seen. Eifts are formed, and these are filled 
with molten matter from below, which forms dikes. 
Sometimes one side of the rift slips down slightly, 
thus forming what in geology is called a “fault.” 
Then the material that wells up forms conical heaps 
on the crust, diminutive volcanoes. If water were 
present, these changes would no doubt be consider¬ 
ably modified, and would still more resemble what 
has occurred on the earth. 
Likewise, in the case of the earth, after a mere 
shell of crust had formed, the inside, cooling, be¬ 
came too small for the outer envelope. As this was 
comparatively thin, and large areas were affected, it 
could not withstand the pressure of its own weight 
and that of the superincumbent atmosphere ; it yielded 
and began to sink at some places, and this pushed it 
up at others. The low places became hollows for the 
oceans, and the ridges were the beginnings of moun¬ 
tain ranges. It is probable that at points the crust 
broke, and the liquid mass from below was forced up 
through the rifts and formed active volcanoes. I 
imagine that the little continents just born out of 
the universal ocean sent up curling smoke from more 
than a hundred little cones—the world’s first fur¬ 
naces. 
The water was still hot, and contained much acid. 
Dense clouds obscured the orb of day—it was con- 
