Geology and Natural History. 229 
of the earth’s crust, especially in regions where terrestrial heat isa 
little elevated, giving the moisture special energy in effecting 
mineral changes. 
2 
there can be no doubt. But though, from the evidence of the 
deposits themselves, it,appears impossible to arrive at any abso- 
geological position we might ascertain some ond which 
a be carried, and thus be enabled to assign an 
extreme limi eir antiquity. I believe that I am right in 
interglacial period. I must confess that, wit e 
do not regard this question as conclusively settled by 
any such isolated piece of evidence; and t whatever further 
testimony may eventually be adduced as to so 
tion of this cou try by man, there are, in my opinion, possibilities, 
rticular case, of the. clay being either to 
reconstituted en accidentally redeposited, which make it 
districts which were never overwhelmed by the confluent ice 
masses, and in regions which were not submerged during the last 
