G 
AMERICA THE OLD WORLD. 
ocean washed over the consolidated crust of the 
globe, it would begin to abrade the surfaces upon 
which it moved, gradually loosening and detach- 
ing materials, to deposit them again as sand or 
mud or pebbles at its bottom in successive layers, 
one above another. Thus, in analyzing the crust 
of the globe, we find at once two kinds of rocks, 
the respective work of fire and water : the first 
poured out from the furnaces within, and cool- 
ing, as one may see any mass of metal cool that 
is poured out from a smelting-furnace to-day, 
in solid crystalline masses, without any division 
into separate layers or leaves ; and the latter in 
successive beds, one over another, the heavier 
materials below, the lighter above, or sometimes 
in alternate layers, as special causes may have 
determined successive deposits of lighter or heav- 
ier materials at some given spot. 
There were many well-fought battles between 
geologists before it was understood that these 
two elements had been equally active in building 
up the crust of the earth. The ground was hotly 
contested by the disciples of the two geological 
schools, one of which held that the solid envelope 
of the earth was exclusively due to the influence 
of fire, while the other insisted that it had been 
accumulated wholly under the agency of water. 
This difference of opinion grew up very natu 
rally ; for the great leaders of the two schools 
