78 
ration of rain by this means very much resembles the well- 
known process, in which vapour raised by the agency of the 
sun’s heat from the ocean-surface in the torrid zone is con- 
veyed by the atmosphere and deposited in the temperate zones). 
According to our hypothesis, the downfall of rain would con- 
tinue till, by the mixture of atmospheric currents and the 
flowing of streams of water from the rain over the land, the 
temperature, so far as it depended on the access of central 
heat, was equalized at the earth’s surface, and an equilibrium 
established between the temperatures of the contiguous parts 
of the air and ocean. The evaporation would then cease. 
According to the narrative in Genesis, the rain ceased at the 
end of forty days. 
But what, under these circumstances, would be the effect 
produced on the earth’s envelope, regarded as composed of 
solid and watery parts, and floating on a liquid sea? It is 
plain that by reason of the diminution, by the evaporation, of 
the weight of the waters resting on the bed of the ocean, and 
the increase of the weight of the continents by the accession 
of the deluge of rain, the previously existing conditions of 
equilibrium would be violated, and motion of some kind must 
ensue, and would continue till new conditions of equilibrium 
were established. It will be seen that the forces which, 
according to this view, produce the disturbance of equilibrium, 
act analogously to those which came under consideration in 
the foregoing theory of volcanoes and earthquakes ; and from the 
results observed to take place under the actual physical con- 
ditions of these phenomena, we may infer what might be the 
consequences of an analogous action under the hypothetical 
conditions of the present theory. For instance, we may con- 
clude analogically from facts such as those stated in pp. 73 and 
74, that there might be elevations and subsidences of the earth’s 
crust, the parts which receive an accession of weight being 
depressed, and those from which weight is removed being 
elevated. The application of this principle to our problem 
leads to a very remarkable result, which it will now be proper 
to point out. 
The diminution of pressure at the bottom of the ocean, in 
consequence of the abstraction of fluid matter by the evapora- 
tion at the surface, will give rise to an excess of upward 
pressure of the liquid mass below, and on the other band, the 
increment of the aggregate weight of the continents by the 
fall of rain will produce an excess of downward pressure. So 
long as the solid parts of the envelope retain their form, these 
two pressures only put it into a state of strain. But because 
