118 
AMERICAN GEOLOGY. 
find the primal cause; and it is no disparagement to the intel¬ 
lectual power of man to acknowledge, that respecting the 
primal cause we see only the hand of infinity who kindled the 
once blazing fires of the universe of matter. How or when, 
are questions too deep for us to answer. We may therefore 
regard the primal cause as the remains of that original incan¬ 
descent state, and it is the prolonged activity only of the burn¬ 
ing mass which has but just retired to the deeper parts, above 
and around which the crust has become scaled as it were by 
simple cooling. 
As terrestrial volcanic action is to us the most interesting of 
geological phenomena, this circumstance alone has led both 
geologists and astronomers to scrutinize with great care the 
only heavenly body which admits of examination, in order to 
ascertain if our satellite shows indications of the same agencies 
of which I am speaking. The result of these examinations 
has clearly proved that the moon has been the theater of 
intense volcanic action. This luminary, which shines with 
such silvery light, and appears so plane and even, becomes un¬ 
der the telescope studded with rough and rugged mountains, 
whose tops are crateriform, or its planes have the semblance 
of deep excavations, in which are standing sharp conical peaks, 
perforated like the cones of Vesuvius, Etna, and Cotopaxi, 
Our satellite, then, is but a smaller pattern of the earth, 
exhibiting, an intenser volcanic action than that of the earth— 
a fact which is probably due to the absence of water, an 
agent which upon the earth has modified its surface so far 
as to conceal in part beneath the sedimentary rocks its original 
volcanic nature. The moon, however, presents its face covered 
with ancient eschars, which time never has healed, and which 
are destined to remain in all their original roughness and 
rigidity. 
In illustration of lunar volcanic phenomena, I have presented 
the student with a crystallotype of her surface, which was taken 
by Mr. Whipple with the Harvard telescope. It will be 
observed that her surface is studded with prominences which 
