After leaving Ayrshire he was transferred to Kelso, and subsequently to the district ranging from Perth to Dunkeld. From a geological point of view this ground was considerably less varied; but as his note-books show, he was by this time deeply absorbed in glacial and Pleistocene geology, and every scrap of information regarding the latest stages in the physical history of Scotland was most carefully recorded and its importance weighed. Many of the conclusions he had already arrived at in Ayrshire were confirmed by fresh evidence in these years. And the estuary of the Tay, with its rich succession of late-glacial and post-glacial accumulations, became of great importance in his interpretation of the “glacial succession,” a subject to which the remainder of his life was devoted more than to any other.
The circumstances that determined his bent towards the investigation of glacial geology cannot perhaps be fully elucidated now in the absence of any statement from his own pen, but it is not difficult to find many reasons that may have influenced him. In considering this subject we may glance briefly at the state of knowledge of this department of geology at the time when he began field work. The years 1861 to 1865 saw a very remarkable development of interest in glacial geology, occasioned by a sudden appreciation of the importance of many facts previously well known but imperfectly understood. Many active geologists in Scotland were coming for the first time to adopt the views which have ultimately obtained acceptance in regard to the Pleistocene history of Scotland, and the change of opinion which was going on was somewhat similar to the still greater change which took place when evolution first began to take the form of a working hypothesis or even an established law of Nature, and to sweep away a great many honoured and treasured theories that had long held sway over the minds of men.
The superficial deposits of sand, clay, and stones that cover the solid rocks in the lower grounds of Scotland, often to a depth of many feet, were considered by most geologists as being of somewhat mysterious origin. It was well known that they contained boulders transported from a distance. Around Edinburgh and Glasgow, for example, large blocks of rock which must have been carried from the Southern Highlands, fifty miles or more, were familiar to those interested in geology. That the surfaces of the rocks on which the drift or boulder-clay rested were striated, grooved, and fluted, was also a well-known fact. Early in the nineteenth century a favourite explanation of these deposits, which had been supported by the celebrated Dean Buckland, was that they were the remains of the Deluge as described in Genesis. This theory, however, was soon discarded though the name “Diluvial,” still used by some writers to designate these strata, bears witness to the former acceptance of that hypothesis. For a long time they continued to be considered as flood deposits, laid down by “debacles” of obscure origin. No rational explanation for these powerful “waves of translation” could be formulated, and they failed completely to account for the remarkable scratched surfaces on which the boulder-clay rested. As the study of glaciers advanced, it became clear that moving ice, bearing debris with it, could produce striations exactly like those in question, and the boulder-clay gradually came to be considered a glacial deposit. Very important confirmation of this hypothesis came from the observations of Mr Smith of Jordanhill on the recent shelly clays of the west of Scotland. Many of the mollusca which these clays contained proved to be of species now living in Arctic seas, and the inference was obvious that at no very distant epoch a glacial climate had prevailed in Scotland. About the year 1837 Agassiz had been led by his investigation of the boulder-clay of Switzerland to the conclusion that at one time the glaciers had extended far beyond their present limits, and had covered the plains at the foot of the Alps with a vast confluent sheet of ice. Agassiz, in 1840, visited Scotland with Dean Buckland, and as the result of his observations had not hesitated to declare that Scotland also had been swathed in an ice-sheet. British geologists, however, were slow to accept his conclusions, and the favourite explanation of the “drifts” was that they had been laid down at the bottom of a sea in which icebergs floated, transporting great rock boulders from one place to another.
In 1866 the veteran geologist Charles Maclaren, then at the age of eighty-four, published the second edition of his Geology of Fife and the Lothians, and in his account of the “alluvial phenomena” of the district he shows the transitional state in which opinion then was passing from the iceberg hypothesis to the land-ice hypothesis. “The dressed surfaces as well as the ‘Till’ or Diluvium [the lower boulder-clay] seem to have been mainly due to a great envelope of ice acting for ages; the newer alluvium, on the other hand [the upper boulder-clay], appears to have been chiefly due to icebergs and ocean currents. In thus attributing so much to the action of ice during a long glacial period, it must ever be borne in mind that oceanic currents preceded this ice action, and that similar currents must have been in existence to transport the icebergs to which we ascribe the erratic blocks and boulders. Alternate submergence and elevation of the north of Europe, combined with ice on land and ice on water (in my opinion), must satisfactorily explain these diluvial phenomena, which, as unsettled problems, are still engaging the attention of younger geologists.”
One of the ablest champions of the land-ice hypothesis was Robert Chambers, who was widely known as a historian and a member of the famous Edinburgh publishing firm. As early as 1852 he ranged himself on the side of Agassiz, declaring that floating icebergs and currents of water could not possibly be accepted as a satisfactory explanation of the boulder-clay and striated rock-surfaces. Mr T. F. Jamieson of Ellon was making a very careful study of the drifts of Aberdeenshire and the adjacent counties, and had little hesitation in accepting the theory of an extensive ice-sheet, covering these districts and filling up all the valleys, as the explanation most in accordance with the facts which he had observed. He admitted, however, that subsequently there had been a great submergence during which many of the uppermost drift deposits had been laid down.
Sir Charles Lyell, whose authority on questions of theoretical geology at that time was paramount, was also willing to accept the former existence of glaciers over very extensive regions of the British Isles, and described moraines that occur in the upland valleys of Forfarshire, though he considered the drifts of the lower grounds as mainly at any rate deposited in cold seas in which icebergs floated. Much more important than Lyell, or at least much more likely to exert influence on the mind of James Geikie at an early stage in his career, was Sir Andrew Ramsay, then local Director of the Geological Survey. Ramsay was a man after James Geikie’s own heart, and there can be no doubt that his influence on Geikie was very great. We should not be far wrong, in fact, in regarding Geikie as the direct successor of Ramsay in the line of scientific thought. Through his whole life James Geikie hardly departed from the position taken up by Ramsay on glacial geology, though of course he developed many new and important fields of investigation. There was a remarkable similarity in their outlook; they both relied on very much the same class of evidence, depending specially on field geology as a basis, but prepared to build up far-reaching deductions from the facts they had observed. Most of the theories enunciated by Ramsay were strongly and consistently maintained by James Geikie up to the close of his career. Ramsay also was more than a glacialist. He left a deep mark in the study of physiography, the origin and history of British scenery, and in structural geology; and in these subjects also James Geikie found continual inspiration.
When Geikie joined the Survey, Ramsay was at the zenith of his powers. He had been for twenty years an active field-geologist on the Survey staff; had travelled very extensively over Great Britain on geological work; was a well-known man in London scientific circles; and from his official position had unrivalled opportunities of making himself acquainted with the field evidence bearing on all geological questions then under review. He was endowed with great energy and a warm imagination; a genial and hearty comrade, very fond of a joke; well read in poetical and romantic literature; but withal a hard, untiring worker who never spared himself or any member of his staff where duty was concerned. The two men were in many ways alike, and no doubt they were very soon on terms of close friendship; and to the latest days of his life James Geikie spoke of Ramsay with deep affection and respect.
To the influence of Ramsay we must add that of his brother. Archibald Geikie was already widely known for his geological work, and second only to Ramsay as an authority on theoretical questions affecting British geology. He had been appointed to the staff of the Geological Survey in 1855, six years before James Geikie, and had rapidly risen into prominence. Although at first he had given his adhesion to the iceberg theory, his views had changed under the influence of Ramsay, and in a classic paper which he read to the Geological Society of Glasgow in 1862 he had described the glacial deposits of Scotland in an exhaustive manner. This paper, so full in its details and so lucid and moderate in statement, produced a great impression, at any rate in Scotland, and clearly marked out the way along which future progress was to be made. Though Sir Archibald Geikie subsequently made few contributions to glacial geology, deserting this field for the study of volcanoes, and of other parts of physical and historical geology, he did a very great service to science in so clearly defining his position on a much debated subject by publishing this paper.
As time went on, some of the younger geologists who had joined the Survey after James Geikie became enthusiastic workers at glacial science, and came to earn a reputation only second to Geikie himself in this department of geology. Of these, we may specially mention Dr John Horne and Dr Benjamin N. Peach, both of whom became eminent authorities on the glacial geology of Scotland. In early years they were James Geikie’s most intimate friends; their observations were always at his service, and their criticism and advice he greatly valued.