Elizabeth Cary Agassiz, Louis Agassiz: his life and correspondence, third edition

[308] and grooves; the polished surfaces, the roches moutonees; the rocks, whether hard or soft, cut to one level, as by a rigid instrument; the unstratified drift and the distribution of loose material in relation to the ancient glacier-beds,—all agreed with what he already knew of glacial action. He visited the famous ‘roads of Glen Roy’ in the Grampian Hills, where so many geologists had broken a lance in defense of their theories of subsidence and upheaval, of ancient ocean-levels and sea-beaches, formed at a time when they believed Glen Roy and the adjoining valleys to have been so many fiords and estuaries. To Agassiz, these parallel terraces explained themselves as the shores of a glacial lake, held back in its bed for a time by neighboring glaciers descending from more sheltered valleys. The terraces marked the successively lower levels at which the water stood, as these barriers yielded, and allowed its gradual escape.¹ The glacial action in the whole neighborhood was such as to leave no doubt in the mind of