216 
GEOLOGY OF THE FIRST DISTRICT. 
15. Others have attributed the effects to a change in the axis of rotation of the earth;* and 
others, still, to the collision of a comet with the earth.! 
It will be observed that the theories adduced are nearly all calculated to explain facts that 
are more or less local, and many of them offer a sufficient and apparently a philosophical 
explanation of the region to which they apply ; but the facts now known, show that the cause 
was not confined in its action, as was at one time supposed, to the region of the Alps, then 
to the northern part of the Eastern Continent, and afterwards to the northern part of the 
Northern Hemisphere ; but from the knowledge now possessed, it is believed to have acted 
with equal force, and over an equal extent of the Southern Hemisphere. We must then seek 
for some cause which shall have affected the earth, and which is capable of explaining in a 
philosophical manner the various effects produced over such vast areas of the earth’s surface. 
It may be here premised, that the nature of the case is such, that the evidence cannot be 
direct, but is necessarily presumptive, and confined to reasoning from effects to their causes, 
and inferences from facts considered as well as established, and from the recognized laws of 
nature. If these, or any of them, should not prove true, the superstructure built upon an 
unstable foundation must necessarily fall, and the theory that will be proposed, like those that 
have preceded it, must add one more to the numerous theories that have been framed to 
account for the various phenomena of geology, and found, as knowledge progressed, to be 
insufficient. 
The following propositions are necessarily preliminary to the farther consideration of the 
subject; 
1. The earth is in the state of a cooling body, 
2. Cooling bodies diminish in volume. 
3. Bodies revolving on axes, or in orbits, by a diminution in their diameters or their orbits, 
increase in their velocities of rotation. 
4. An increase in the velocity of rotation implies an increase in the centrifugal force. 
5. An increase of centrifugal force tends to cause a greater oblateness in the spheroidal 
form of a revolving spheroid. 
6. The earth is an oblate speroid, of such a form as is due to a fluid body revolving with 
its present velocity. 
The above are admitted philosophical truths and laws of nature. 
If it can now be shown that the earth has diminished in volume, it would demonstrate that 
there has been a flow of water from the polar regions towards the equator, to restore the equi¬ 
librium that would necessarily follow on such a body, of which a part of the surface is fluid, 
revolving with an increased velocity ; or reciprocally, if it can be shown that there has been 
Appleton. American Journal of Science, Vol. 11, pp. 103, 104. 
t Halley’s Essay on the Cause.s of the Flood, in 1694. 
