Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/50

 transporting huge blocks of stone, and in depositing vast mounds of rubbish, are illustrated by him from many an Alpine valley. Recalling the original observations of Playfair, he points out how clear is the evidence for the former wide extension of the glaciers of Switzerland. In short, his eye seems ever to have been upon the watch for every phenomenon bearing upon the mutations of the existing surface of the land.

The lessons which he had thus laboriously learned among the living ice -rivers of the Alps bore fruit when he came again to wander among the more mountainous regions of his own country. In the year 1840 Agassiz had made the startling announcement that the British islands had once been deeply buried under a vast mantle of snow and ice, and that the traces of its seaward motion were yet fresh and clear upon the sides of many valleys among the uplands. Following up the observations of the Swiss naturalist, Buckland and Lyell had pointed out the former existence of glaciers in the Highlands and other parts of the country. When, however, we look back upon the early discussion of this subject, we are forced to admit that conclusions were often based upon very hasty and imperfect observations. In particular, glacier moraines were often recognized in places where no geologist would now be able to find them. Much as Forbes knew of the geological effects of ice, his natural caution kept him from taking part in this discussion for a time, until he was able to produce more accurately determined data than had, in many cases at least, been available. In the year 1845 he visited the Isle of Skye; and his eye, already trained to recognize the traces of vanished glaciers in Switzerland, was at once struck by the identity of the forms assumed by the rocks at Loch Scavaig with the roches moutonnees of the Alps. Further investigation led him to obtain complete demonstration of the former presence of a group of glaciers descending from the rugged scarps of the Cuchullin Hills. He walked over mountain and glen, filling in a rough sketch map of the glacier valleys as he went along, and in December of the same year he read a narrative of his observations to the Royal Society of Edinburgh. This was the most detailed and satisfactory account which had yet been given of the proofs that the Highlands of Britain once nourished groups of glaciers.

In the year 1851 Professor Forbes undertook a journey to Norway, partly to make observations of the great solar eclipse, and partly drawn by his love of physical geography, and notably of glaciers. It was his design to compare the phenomena of glaciers in Northern Europe with those already so familiar to him in Switzerland. This he has done in a masterly way. His pages contain, in a clear and succinct form, the sum of all that was known at the time regarding the snow-line and the existing glaciers of Norway. I have myself gone over much of the ground he has described, and can bear witness to the accuracy of his sketches, alike of pencil and of pen.. His two chapters on the physical geography of Norway have always appeared to me to be a masterpiece of careful yet rapid observation, broad generalization, and clear description.