Nczv Hypothesis of llarfh-Origin. — Fairchild. iii 
Professor Chamberlin has shown how submergence of tlie 
continental borders favors hmestone accumulations which in 
turn causes enrichment of the ocean and air in carbon dioxide, 
since the limestone fixes only one equivalent of the carbon di- 
oxide, and releases one of the water, from the bicarbonate held 
in solution. For example, the warm and probably moist cli- 
mate so widespread in the mid-Carboniferous followed the 
long submergence and limestone-making of the sub-Carbon- 
iferous ; and that of the Tertiary succeeded the limestone depo- 
sition of the Mesozoic and Eocene. 
If the salt deposits of the Cambrian and later time are an 
evaporation product then certainly the atmosphere of those 
early times did not contain the carbon dioxide which has been 
stored in the later strata. These two sets of facts, the vast 
quantities of stored carbon and the ancient salt deposits are 
discordant under the old hypothesis. The new hypothesis 
on the other hand gives a satisfactory explanation for both 
classes of phenomena. 
GLACIATION. 
It is beyond the plan of this paper to discuss at length the 
phenomena of glaciation under the new hypothesis, since it 
has already been traversed by our leader in this field. Briefly 
it may be said that glaciation is not the remarkable and unusual 
phenomenon it was once thought to be, but ma}^ have occur- 
red even in early geologic time. The conditions, geologic and 
meteoric, requisite for glaciation do not seem to be extraordin- 
ary. Glaciation is essentially a local phenomenon, a fact which 
w^as not formerly appreciated. Cyclonic circulation of the at- 
mosphere, which localizes and concentrates the precipitation, 
with just sufficient cold to produce snow instead of rain, may 
initiate a snow field, the perpetuation and extension of which is 
an ice body. A cause of general low temperature would seem 
to be the reduction in amount of atmospheric carbon dioxide. 
The extent and altitude of the land masses probably have an 
indirect influence by determining the great barometric areas 
and the paths of cyclonic storms. It is possible that the at- 
titude of the earth toward the sun may have some efYect and 
that the precession of the equinoxes might, at a critical time, 
help to produce the alternation of glacial with intorglacial 
epochs. It is probable that glaciation is not a simple effect, but 
