70 SECTIONAL ADDRESSES. 
lithosphere which projects above sea-level is extremely small when 
compared with the volume of the whole globe. 
It is well known that the power of erosion is sufficiently great to have 
reduced this relatively small mass to sea-level time and time again through- 
out the long course of the geological ages. Nevertheless, it is confidently 
believed that this result has never been entirely achieved. Rejuvenation 
has kept pace with erosion throughout the hundreds of millions of years 
that the earth has endured. In my opinion this marvellous nicety of 
adjustment between two great sets of opposing forces is one of the major 
lessons of geology. Is it a mere coincidence or is it evidence of design ? 
Climate. 
That the earth has experienced great changes in climate is a deduction 
from geological observation that is universally admitted. Many are the 
possible causes of change and voluminous is the literature of the subject. 
Cosmical controls such as changes in the sun’s radiant energy and in the 
earth’s planetary motions have been adduced; appeal has been made 
to variations in the composition of the atmosphere and to changes in the 
distribution of land and sea with all the consequent effects on atmospheric 
and oceanic circulation; terrestrial heat, radioactivity, and vulcanism 
are thought to have played a part ; and a theory has been brought forward 
that in earlier times solar control was a negligible factor. 
Whatever the causes, climate has been extremely variable in past 
time; the polar regions have been temperate—almost tropical—and 
ice sheets have extended over sub-equatorial regions. It is significant, 
also, that a given climatic condition in a given locality is not necessarily 
of long duration. Great changes are known to have occurred within the 
time of man, and the warm interglacial periods of the Pleistocene alter- 
nated with glacial conditions within comparatively short bounds. 
Climatic change must be regarded as an ever-present factor. It is 
highly probable that variation in climate will greatly affect the activities 
of the human race within a measurable number of years, and it is not 
impossible that the sites of our present centres of civilisation will be buried 
under glaciers and that a new civilisation will occupy, under a genial 
climate, the present inhospitable regions around the poles. 
Despite the changes in any given locality, the continued existence of 
life is sufficient evidence that the whole globe has not experienced, from 
the earliest geological time, any very great universal change in climate. 
Griiner has proved to the satisfaction of most geologists the existence of 
alge in the Keewatin of Minnesota. The great masses of limestone with 
disseminated graphite of the Grenville are at least suggestive of life, and 
Moore has brought forward convincing evidence of alge in the Animikie © 
of Belcher Islands in Hudson Bay. Both the Archzozoic and the Pro- 
terozoic, therefore, were warm enough to permit organisms to exist despite 
the intervening event of an ice age in the Huronian. 
Wonderful have been the changes in climate and far-reaching their 
effects, but truly marvellous has been the continuity of a range of tempera- 
ture permitting the existence of life from the very dawn of earth history 
to the present moment, Nothing short of a cosmical catastrophe can alter 
a condition that has maintained for nearly two billions of years. Surely 
if culture is the cultivation of the spirit, the contemplation of geological 
