Biographical Notice of James Croll, published in History of the Geological Society of Glasgow, 1858 – 1908, with Biographical Notices of Prominent Members, edited by Peter MacNair, F.R.S.E., F.G.S., and Frederick Mort, M.A., B.Sc., F.G.S., F.R.S.G.S., Honorary Secretaries.
Published by the society, at its rooms, 207 Bath Street, Glasgow, in 1908.
JAMES CROLL, LL.D., F.R.S.
James Croll was one of the early members of the Glasgow Geological Society, who ultimately achieved a wide reputation in virtue of his researches on the probable cause of climatic change.
Born in 1821 at St. Martin’s, Perthshire, he encountered great difficulties, like many Scotsmen, in the early part of his career. For years he tried various occupations with indifferent success, and at last obtained an appointment in the Andersonian University, Glasgow, which proved the turning point of his life. It placed within his reach the University Library and the Library of the Philosophical Society, Glasgow. It gave him leisure to pursue those studies on electricity, heat, and the physical causes of climatic change, which formed the subjects of his earlier papers. It brought him into contact with the founders of the Glasgow Geological Society, with whose aims he strongly sympathised. He took special interest in all questions connected with the glaciation of the country, for he realised that the iceberg theory was doomed, and that nearly twenty years had been lost by geologists, owing to their refusal to adopt the suggestions of Agassiz regarding the former extension of land ice in Scotland.
Accepting the land ice origin of boulder clay and moraines, Croll proceeded to deal with the question of the probable causes of climatic change. His first contribution to this subject was published in 1864, which immediately arrested the attention of Lord Kelvin, Sir Andrew Ramsay, and Sir Archibald Geikie. Through their instrumentality he was appointed Secretary to the Scottish staff of the Geological Survey in 1867 – a position which he held till his retirement in 1881.
His researches on the probable causes of climatic change extended over a period of eleven years, and were published in 1875 in one volume entitled “Climate and Time.” This work embodies Dr. Croll’s main contributions to the scientific research of his time. His contention was that glacial cycles arise indirectly from cosmical causes. He investigated the problem of the eccentricity of the earth’s orbit and its physical relations to the Glacial period. By means of Leverrier’s formulae, he calculated tables of eccentricity for three million years in the past and one million years in the future, with the view of determining periods of high eccentricity, which, according to his theory, were coincident with cycles of extreme cold.
He next pointed out the various physical agencies affecting climate resulting from periods of high eccentricity, of which by far the most important is the deflection of ocean currents. He called special attention to the influence of the Gulf Stream as an agent in the distribution of heat on the surface of the globe. He held that a high condition of eccentricity produces an accumulation of snow and ice on the hemisphere whose winter occurs in aphelion, and that opposite effects supervene on the other hemisphere which has the winter in perihelion. When the northern hemisphere is being cooled, the north-east trade winds far exceed in strength the south-east trade winds, and thus deflect the Gulf Stream into the Southern Ocean. The deflection of this warm current, combined with other causes, would place Europe under glacial conditions, while the temperature of the Southern Ocean would be raised.
In addition to the numerous memoirs bearing on the physical causes of climatic change, he pursued other lines of research, to some of which brief allusion may be made. He tried to determine the present rate of subaerial denudation by ascertaining the quantity of sediment annually carried down by the river systems, and he further showed the value of this method as a measure of geological time. He was the first to suggest that the Scandinavian and Scottish ice-sheets coalesced on the floor of the North Sea, moving westwards towards the Atlantic, thus accounting for the marine shells and boulders of Secondary Rocks in the Caithness boulder clay. He investigated the cause of glacier motion, and advanced an ingenious explanation of his own. He also attributed the submergence during the Glacial period to the displacement of the earth’s centre of gravity by a polar ice-cap.
At the close of his life he reverted to those philosophical questions which had attracted him in his early years. In his last work, “The Philosophical Basis of Evolution,” issued before his death, he contended that the production of motion and the determination of motion were essentially different. He associated the phenomena of evolution with this continuous direction of motion, which, to his mind, implied will and purpose.
A comprehensive autobiographical sketch and memoir of James Croll’s life and work, published in 1896, can be found on the Internet Archive, while a more modern account of his life and appraisal of his contribution to the development of astronomical theory of climate change can be found in the following book:
Imbrie J. & Imbrie K.P. (1979) Ice Ages. Solving the Mystery. Harvard University Press.