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profess to be able to state how such changes are produced ; but 
that, as matter of fact, the heat of large masses is subject 
occasionally to abnormal augmentation, may be inferred from 
what is observed of certain stars, which have been seen to blaze 
out for a time, and then relapse into their previous degree of 
brightness, or to become altogether evanescent. To account for 
variability in the thermal conditions of the solar system, and, 
inclusively, of the earth’s central heat, some physicists have sup- 
posed that there are different degrees of temperature in different 
regions of space, and that the sun, in consequence of its ascer- 
tained proper motion, passes with its attendant planets sometimes 
through a hot region, and at other times through a cold one. 
Without entering into details which would be inappropiate in 
this essay, I could not give the reasons which dispose me to 
assent to this view ; and after all, since the destruction of the 
human race by a deluge must be looked upon as a special act 
of divine judgment, the truth may be that the primary physical 
cause was simply an effect of miraculous interposition. I shall 
therefore content myself with saying that the subjoined expla- 
nations rest on the hypothesis that the Deluge was produced by 
physical causes, which primarily were due to a paroxysm of the 
earth’s central heat. We have, therefore, now to inquire in 
what manner the recorded phenomena of the Deluge might have 
been thus produced. 
It is not difficult to infer, from known physical laws, what 
would be the general result of a sudden increment of the heat 
of the earth’s central mass. The effect of an increase of con- 
siderable amount would in a short time become perceptible at 
the surfaces of seas and oceans, because it would be conveyed 
from their lowest parts by convection as well as by the slower 
process of conduction ; whereas the visible effects of the heat 
on the solid parts of the envelope would be transmitted to- 
wards the surface mainly by conduction. The consequence 
would be that from the whole extent of water-surface a rapid 
evaporation would take place, which would load the superin- 
cumbent air with so much vapom 4 that the ordinary state of 
atmospheric equilibrium would be distui’bed, and air and 
vapour together would be compelled to flow towards the con- 
tinental parts, where little or no evaporation is going on. 
According to what has just been said, those parts and the 
incumbent columns of air would for a time be nearly free 
from the influence of the central heat, and thus the overflow 
would bring air saturated with vapour into contact with colder 
air, in consequence of which the vapour would be condensed 
and fall on the continents in the form of rain. (The gene- 
