process.

But there was another element without the globe, equally powerful in
building it up. Fire and water wrought together in this work, if not
always harmoniously, at least with equal force and persistency. I have
said that there was a time when no atmosphere surrounded the earth; but
one of the first results of the cooling of its crust must have been
the formation of an atmosphere, with all the phenomena connected with
it,--the rising of vapors, their condensation into clouds, the falling
of rains, the gathering of waters upon its surface. Water is a very
active agent of destruction, but it works over again the materials it
pulls down or wears away, and builds them up anew in other forms. As
soon as an ocean washed over the consolidated crust of the globe, it
would begin to abrade the surfaces upon which it moved, gradually
loosening and detaching 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 cooling, as one may see any mass of metal cool
that is poured out from a smelting-furnace today, 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 heavier
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 naturally;
for the great leaders of the two schools lived in different localities,
and pursued their investigations over regions where the geological
phenomena were of an entirely opposite character,--the one exhibiting
the effect of volcanic eruptions, the other that of stratified deposits.
It was the old story of the two knights on opposite sides of the shield,
one swearing that it was made of gold, the oth