446 ELEMENTARY GEOLOGY 
of necessity deposited, just as salt is precipitated from a solution 
in hot water when this is cooled. 
In this ancient period, lava flows were more abundant than 
now, for the crust separating the earth’s surface from the heated 
(then liquid) interior, was much thinner than at present. This 
nearness of heated and even molten rock beneath the crust, 
allowed the latter to fold and move with greater activity than — 
is possible in its present rigid state. It is also probable that the 
temperature of the sun was different from the present, probably 
being higher. Astronomers suggest also that. the tides of early 
times were more powerful, and the days shorter, so that the 
earth was then a very different sphere from now. 
Perhaps in this early time of greater activity of all the agen- 
cies of air, water, and even the earth itself, the Archean rocks 
were formed. It was formerly thought that these really repre- 
sented the ancient and first crust of the earth, and though many 
now question this hypothesis, it cannot even yet be considered to 
be disproved. If our speculation concerning the origin of the 
earth from a liquid condition is correct, there must have been 
a time in the earth’s history when rocks quite lke those of the 
Archean were formed. These would be somewhat like the igne- 
ous rocks; but with the ease of movement of the crust, it is prob- 
able that they would be easily folded and contorted. At the time 
when the hot waters were falling to the surface, their great chemi- 
cal activity and erosive power would cause the accumulation of — 
beds in the ocean, which, heated by lava intrusions and flows, and 
by the liquid rock beneath the crust, would bear very little resem- 
blance to the sediment deposits that are now being accumulated. 
Up to this time no life could exist upon the earth, because the 
temperature of land and water would be above that at which life, 
as we know it, could exist; but the time came when there were 
conditions favorable to life. At first only low creatures could 
exist in the hot and impure waters; and then began that wonder- 
ful series of changes and progressions of animals and plants, 
which is revealed in the later rocks, and which has culminated 
