THE QUARTERLY 
meu NAL, OF (SCLE NCE: 
OCTOBER, 1874. 
BAN EXAMINATION: OF THE: THEORIES 
THAT HAVE BEEN PROPOSED TO ACCOUNT FOR 
fre CLIMATE OF THE GLACIAL PERIOD. 
By Tuomas BELT, F.G.S. 
~ 
ps the speculations I ventured to make ina recent work* 
on some of the phenomena of the Glacial period, I 
purposely avoided entering on the question of the 
cause of the great accretion of ice, believing that the time 
was not ripe for its discussion, and hoping that it might be 
taken up by some astronomer, as it is to Astronomy rather 
than Geology that we must look for a solution of the 
problem. I find, however, that my explanations of the 
facts of the “great ice age” are constantly met by objec- 
tions founded on the theories of the cause of that event; 
and I propose in the present paper to discuss the principal 
hypotheses that have been advanced to account for the 
origin of the Glacial period, and to endeavour to show that 
my speculations on the extent and effects of the ice are in 
accordance with, and a necessary consequence of, the 
theory that is most in harmony with the facts with which 
we have to deal. 
1. Theory of a Change in the Relative Position of the Conti- 
nents and the Ocean.—In that great work the ‘‘ Principles of 
Geology,” in which the foundations of the modern science 
were laid in 1830 by Lyell, and in successive editions in 
which the veteran philosopher has ever kept abreast of 
advancing knowledge, he has brought forward and supported 
the theory that great oscillations of temperature have been 
produced by changes in the relative positions of land and 
water. This theory he has enforced with a wealth of illus- 
tration derived from his vast acquaintance with geological 
and geographical facts, and by the masterly arguments of 
a clear, comprehensive, and judicial mind. Chiefly through 
* The Naturalist in Nicaragua, p. 262. 
VOL. IV. (N.S.) 3H 
