66 REV. PROF. G. F. WRIGHT, ON THE INFLUENCE OF THE 
That these great changes of land level were in some way 
connected with the Glacial Epoch is beyond question. And it 
is not difficult to perceive in the forces connected with this 
remarkable epoch a cause for this unstable condition of the 
earth’s crust so late as that of the pre-historic period of man’s 
existence. During the Glacial Epoch at least 6,000,000 cubic 
miles of ice were piled up over the northern part of America 
and of Europe. For the production of this ice enough water 
would have to be abstracted from the ocean to lower its level 
250 feet the world over. Other high authorities would make 
the amount of ice twice, or even three times, that which we 
have indicated, with a correspondingly larger amount of water 
abstracted from the ocean.* But even on my own moderate 
estimation we have a shifting of weight from the ocean beds to the 
limited area of glaciation amounting to 24,000,000,000,000,000 
tons, equalling the total weight of the North American conti- 
nent. The transference of such an enormous weight from the 
ocean to the continents and its subsequent return to the ocean 
is a force so inconceivable that we cannot estimate its efficiency 
in disturbing the equilibrium of the continents, and causing de- 
pressions and elevations of land out of all analogy to those which 
we have witnessed within the historic period. But pre-historic 
man evidently did witness these disturbances and was pro- 
foundly affected by them. 
Indeed, the story of the Noachian Deluge becomes easily 
credible to the attentive student of the shifting forces at work 
during the glacial epoch ; and the rapidly changing conditions 
to which man was subjected during this trying period of his 
history may readily account, on the principle of Natural Selec- 
tion, for the rapid differentiation of the race in its final 
distribution over the world. 
While the results of our studies in the Glacial Epoch are not 
as definite in their results as one would wish, this important 
conclusion is established, namely, that in the early periods of 
the existence of the human race there was an instability of 
conditions arising from the instability of land levels caused by 
the Glacial Epoch which frustrates all attempts to reason back- 
wards by analogy from present conditions. 
* See Chamberlin and Salisbury’s Geology , vol. iii, pp. 327-502. 
