THEORETICAL GEOLOGY. — INTRODUCTORY. 61 
behold it. It is not states and empires alone that have been torn 
by intestine commotions. The evidence is ample, that the solid 
fabric of the globe has been shaken and rent. The history of 
these changes is brief ; it is written on the stony strata of the 
earth. But if the events recorded are few in number, they are 
attractive from their magnificence. 
In no department of scienee is an acute, but sober and cautious 
judgment more necessary, than in decyphering these ancient 
records. Every character from which valuable information can 
be derived must be passed under review, and the instruction 
elicited which it is capable of conveying. At the same time we 
must be on our guard, and see that fancy does not get the mastery 
over the judgment, lest we find in the present appearances of the 
globe, evidences of changes that have never occurred, and of 
which no indications can be discovered by any eye but ours. 
The nature of the danger, and also of the investigations upon 
which we are about to enter, may be illustrated by an example. 
It is well known that on the banks of the Nile are various fabrics, 
especially temples, and tombs of colossal dimensions, some of 
which stand upon the surface of the soil, and others are excava- 
ted in the rocks under ground. The material of which they are 
formed varies with the geological character of the district in 
which they are. In the southern, or upper end of the valley of 
Egypt, they are hewn out of granite, lower down they are exe- 
cuted in sandstone, and finally we come to the pyramids, built, as 
has been already stated, of secondary limestone. One must have 
been upon the spot if he would have an accurate idea of the vast- 
ness and solidity of these ancient structures. Their walls are 
covered with hieroglyphics. Of the language of the people by 
whom these works were executed, we know next to nothing. 
If they had historians, their works have perished, so that it is 
from "lying Greece," that we have derived the little we profess 
to know respecting them. But we will suppose the light shed 
by Grecian literature upon the antiquities of Egypt, to be extin- 
guished, and that under these circumstances, an intelligent trav*- 
eller passing under the portico of an Egyptian temple, should 
wish to know something of the character, condition, and fortunes 
of the people by whom it was built; there are a few particulars, 
respecting which he would be able to arriye at a good degree 
of certainty. 
He would not, for instance, doubt that there once existed along 
the banks of the Nile, a numerous, industrious and flourishing peo- 
ple, united for a long time under one government. They must have 
been numerous and industrious, or they never would have been able 
to execute such stupendous works. They must have been united 
under one government, because a number of little independent 
states, would never have combined for the erection of so many 
costly structures, and have adhered to their engagements until 
they were completed. The unity of design observable in these 
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