Theories of the Earth's Origin — Upham. 217 
traction, as seems reliably evidenced by the rings of Saturn 
and by the many little asteroids. 
Coming to the question whether the accumulation of 
so large a body as the earth took place without its becom- 
ing intensely hot and molten, somewhat like the sun, we 
have first the observations and theories of geology to aid 
in giving an answer, and these may be advantageously 
supplemented by the phys-iographic features of our satel- 
lite, the moon. It has been long held by geologists that 
the downward increase of heat in the earth's crust, present 
volcanoes, the widely distributed evidences of ancient vol- 
canic action, and thermal metamorphism of great rock 
formations, indicate an internal temperature which must 
fuse any known rocks, unless they are prevented from this 
by overlying pressure. The new hypothesis of Chamber- 
lin accounts for vulcanism, and for all that we know of the 
earth's internal heat, fully as well as the Laplacian hypo- 
thesis of condensation of an intensely hot gaseous nebula, 
while it better accords with the physical and dynamic rela- 
tions of the planets and sun. 
If our inquiry be turned to the moon, we see a most 
wonderful record, as it is generally regarded, of extinct 
volcanic action, implying a formerly very hot and probably 
almost wholly molten state of that globe, which has a little 
more than one-fourth tlie diameter of the earth. These 
two companion globes were doubtless accumulated simi- 
larly. The moon, after acquiring its present size, had 
multitudes of volcanoes which left round craters, or parts 
of their crater rims, of varying dimensions from those at 
the limit of telescopic vision up to one with a diameter of 
about 800 miles, or nearly four-fifths of the moon's radius. 
So great a lake or sea of molten rock, similar to the cal- 
deras of the Hawaiian volcanoes, but of vastlv larger area, 
whose crater rim is partially preserved in the lunar Car- 
pathian-Apennine-Caucasus chain of mountains, could 
only exist when much of the interior of the moon was 
melted. It seems possible and indeed probable, therefore, 
that the earth, whether formed as supposed by the old or 
the new nebular hypothesis, was nearly or quite all melted 
during a considerable part of the time of its accumulation. 
