PRELIMINARY REMARKS, 
17 
there is no discharge or surplus water, the constant evaporation 
of fresh water concentrates the saline matter of the lake, and 
in time it becomes salt. The great salt lake of Utah became 
saline by evaporation of its waters, the evaporation and drain¬ 
age of the valley being sufficient to equalize each other. 
There is a high probability that the saltness of the seas and 
oceans had attained a large amount of saline matter prior to 
the palaeozoic period. The silurian system furnishes brine 
springs, and the fossils of this early period indicate that they 
were the inhabitants of the ocean. The vast quantity of salt in 
the oceans of the globe indicates also the lapse of long periods 
during which the saline matter was accumulating. 
Water separates the parts of rocks from each other. This is 
the result of congelation; this, often repeated, ends in commi¬ 
nution or disintegration. Soils are comminuted or pulverized 
rocks. The process of comminution is more rapid on the tops 
of mountains. Slaty, schistose, and jointed rocks favor this 
result by admitting water between their lamina and joints. 
The broken and comminuted rocks are thus prepared for a 
removal to a lower level. The small but rapid streams first take 
upon themselves this office. A part of the disintegrated rock 
remains upon the tops and sides of mountains. It bears a 
scanty herbage, whose roots confine it more securely. The 
streams lose a portion of their burthen at all the levels, where 
small meadows are formed, and where grass springs up. The 
streams unite in plains below, where a rich vegetation is nour¬ 
ished, and where climate favors the organic kingdoms. The 
united mountain streams form rivers, which flow oceanward; 
but before they reach the great reservoirs, the tides check their 
currents. Here deposits are again made. Shoals are the 
uniform results of the meeting of river currents with the tidal 
wave. But the return tide favors the river current, and its 
detrital matter, which it has borne along, is delivered up to the 
ocean wave. The quantity of earthy matter which is thus 
transported, varies with the season. The Missouri is always 
muddy, and a thick deposit subsides in vessels in which it stands, 
3 
