Some Salient Points in the Science of the Earth

by Sir John William Dawson

[CHAPTER XIII.]

THE GREAT ICE AGE.

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Scientific superstitions, understanding by this name the reception of hypotheses of prominent men, and using these as fetishes to be worshipped and to be employed in miraculous works, are scarcely less common in our time than superstitions of another kind were in darker ages. One of these which has been dominant for a long time in geology, and has scarcely yet run its course, is that of the Great Ice Age, with its accompaniments of Continental Glaciers and Polar Ice Cap. The cause of this it is not difficult to discern. The covering of till, gravel and travelled boulders which encumbers the surface of the northern hemisphere from the Arctic regions more than half way to the equator, had long been a puzzle to geologists, and this was increased rather than diminished when the doctrine of appeal to recent causes on the principle of uniformity became current. It was seen that it was necessary to invoke the action of ice in some form to account for these deposits, and it was at the same time perceived that there was much evidence to prove that between the warm climate of the early Tertiary and the more subdued mildness of the modern time there had intervened a period of unusual and extreme cold. In this state of affairs attention was attracted to the Alpine glaciers. Their movement, their erosion of surfaces, their heaping up of moraines bearing some resemblance to the widely extended boulder deposits, their former greater extension, as indicated by old moraines at lower levels than those in process of formation, were noted. Here was a modern cause capable of explaining all the phenomena. Men's minds were taken by storm, and as always happens in the case of new and important discoveries, the agency of glaciers was pushed at once far beyond the possibilities of their action under any known physical or climatal laws. This exaggerated idea of the action of land ice in the form of glaciers is not yet exploded, more especially in the United States, where official sanction has been given to it by the Geological Survey, and where it has been introduced even into school and college text-books. It affords also a telling bit of scientific sensationalism, which can scarcely be resisted by a certain class of popular writers. America has also afforded greater facilities for extreme theories of this kind, owing to the wide and uninterrupted distribution of glacial deposits, and the more simple and less broken character of its great internal plateau, while the influence of great leading minds, like those of the elder Agassiz and of Dana, naturally held sway over the younger geologists. Fortunately Canada, which possesses the larger and more northern half of the North American continent; though numerically inferior, and therefore overborne in the discussion, has, in the main, remained steadfast to facts rather than to specious theories, and has been confirmed in this position by the clearer testimony of nature in a region where many of the features of the glacial age still persist.[156]

[156] I may refer here to the recent researches of Dr. G. M. Dawson, Mr. R. Chalmers, Mr. McConnell and Dr. Ells.

The writer of these pages has, ever since the publication of the first edition of his "Acadian Geology,"[157] steadily resisted the more extreme views of glaciation, and has opposed the southward progress of the great continental glacier. Though, figuratively speaking, overborne and pressed back in the course of its extension, he has now, like those primitive men who are imagined in the post-glacial age to have followed up the retreat of the ice, the pleasure of seeing the once formidable continental glacier broken up into great local glaciers on the mountain ranges separated by intervening areas of submergence.

[157] 1855.

The questions relating to this subject are too numerous and varied for treatment here. The question of the causes of the great lowering of temperature in the glacial age I shall leave for consideration in the next chapter, and merely state here that I believe changes of distribution of sea and land and of ocean currents are sufficient to account for all the refrigeration of which there is good evidence. I content myself with a comparison of the glacial phenomena of Mont Blanc and of the Gulf of St. Lawrence from my own observation,[158] and some general deductions as to glacier possibilities.

[158] Published in 1867.

A scientific voyager carries with him a species of questioning peculiar to himself. Not content with vacantly gazing at the sea, scrutinizing his fellow passengers, noting the changes of the weather and the length of the day's run, he recognises in the sea one of the great features of the earth, and questions it daily as to its present and its past The present features of the sea include much of surpassing interest, but the questions which relate to its origin and early history are still more attractive. Some of these questions are likely to interest a voyager from Canada entering the Atlantic by one of its greatest tributaries, the St. Lawrence.