34. Agassiz, Louis (1807-1873) 

"The glacial theory and its recent progress." In:  Edinburgh New Philosophical Journal, 1842, vol. 33, pp. 217-283.


The Parallel Roads of Glen Roy, with the former extent of glaciers indicated by dots, and striated rocks by short parallel lines, from Louis Agassiz, “The glacial theory and its recent progress,” 1842.

In the fall of 1840, while his Études sur les glaciers was in press, Agassiz visited the British Isles.  He gave a paper at a scientific meeting in Glasgow, and then, with English geologist William Buckland as his guide, he journeyed northward into the Scottish highlands. 

Everywhere he went, he saw polished and scratched rocks, and erratic boulders, indicating to him that the land had once been covered by glaciers.  And when he got to the Parallel Roads of Glen Roy, he immediately saw what had caused them.  In former times, a glacier from the mountain Ben Nevis had dammed up the Glen, which filled with a glacial lake. 

The Roads were shorelines, but of an ice-dammed lake, not a marine sea, as Darwin had proposed.  He pointed out to Buckland, the moraines, scratches, and erratics, which were mute but certain evidence of the past presence of glacial ice.

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