198 
came before the world no one ever thought of such a thing. Darwin, when he 
wrote the fourth edition of his “ Origin of Species,’^ saw no way out of this 
glacial difficulty ; and he is entirely indebted to Dr. Croll, who came 
forward just in time to help him.* Dr. CrolFs hypothe.sis is that the 
eccentricity of the earth’s orbit will give a certain period of glaciation for 
each hemisphere. Is it so ? The eccentricity at the time assigned to the 
last Glacial epoch was ten and a half millions of miles ; that does not 
mean that the earth was ten and a half millions of miles further from the 
sun than it would have been in a circular orbit, but five and a quarter 
millions of miles further at one part of its orbit and five and a quarter 
millions of miles nearer to the sun at the other part of its orbit. I fancy that 
any mere common-sense person, looking at this, would require a little further 
explanation before he could see how this alteration could produce the Glabial 
period. Dr. Croll said that this would not do alone, it would only be the 
hemisphere that has its winter solstice at a time of great eccentricity that 
would be so glaciated. It is a question whether the distance from the 
sun would have made any diflerence at aU ; but, if it be granted that it 
would, the northern hemisphere, which was supposed to have had its winter 
solstice at the greatest distance from the sun, would, wffien it came to the 
other side of its orbit, get its summer when nearest to the sun, so that, if 
an increased cold is obtained in the winter wffien in aphelion, it has, on the 
other hand, an increased heat at the time it is in perihelion : how this 
could produce the Glacial epoch I am at a loss to see. I\Ir. Croll says, there 
would be a cool atmosphere in summer from the melting of the snow and ice, 
and, on account of this, the earth would pass through a hot summer without 
feeling the heat. But this is merely begging the question. We have not got 
the snow and ice, to begin with ; we know that it is not one winter’s cold 
that would produce the Glacial period, and that what winter w^ould do in 
one part of the earth’s orbit the summer would undo in the other.f The 
difference in climate referred to by Mr. Griffiths, within one hundred miles, 
Avas occasioned by diflerence of altitude ; and the Indian corn to which he 
alludes, Mr. Darwin says, has its roots in ancient glacial moraine. Mr. 
Mello’s letter refers to there being evidence of certain of the fauna liviug 
from the pliocene to the present time. I expected that question would 
be raised, and no one could deal with it better than our friend, Mr. Charles- 
worth. He is a thorough geologist, and I remember how in this room he 
dealt with the pliocene badger, which Avas supposed to have been one of 
those animals which existed in the fauna of both strata — the pliocene and 
the pleistocene. Mr. Charlesworth, however, shoAved that the badger had 
merely worked his way into a pliocene quarry. What really is the 
evidence of pliocene forms now living ? Does the evidence come from the 
* “ It formerly appeared to me that we could not avoid the conclusion 
that the temperature of the ivhole ivorld had been simultaneously loAvered 
during the Glacial period.” — Origin of Species, fifth edition. 
t See The Geological Evidences of the Antiquity of Man re-considered. 
T. K. Callard, pp. 16-26. 
