by a vast glacier, which flowed down its entire length from Mont Blanc to the plain of Piedmont, remained stationary, or nearly so, at its month for many centuries, and deposited there enormous masses of débris. The length of this glacier exceeded 80 miles, and it drained a basin 25 to 35 miles across, bounded by the highest mountains in the Alps. It did not fill this basin. Neither the main stream nor its tributaries completely covered up the valleys down which they flowed. The great peaks still rose several thousand feet above the glaciers, and then, as now, shattered by sun and frost, poured down their showers of rocks and stones, in witness of which there are the immense piles of angular fragments that constitute the moraines of Ivrea.[1] The wine which is drunk in that town is produced from soil that was borne by this great glacier from the slopes of Monte Rosa; and boulders from Mont Blanc are spread over the country between that town and the Po, supplying excellent materials for building purposes, which were known to the Romans, who employed them in some of their erections at Santhia.[2]
The moraines around Ivrea are of extraordinary dimensions. That which was the lateral moraine of the left bank of the glacier is about thirteen miles long, and, in some places, rises to a height of 2130 feet above the floor of the valley! Professor Martins terms it "la plus elevee, la plus reguliere, et la mieux caracterisee des Alpes."[3] It is locally called la Serra. The lateral moraine of the right bank also rises to a height of 1000 feet, and would be deemed enormous but for the proximity of its greater comrade; while the terminal moraines cover something like twenty square miles of country.
The erratic nature of the materials of these great rubbish-heaps was distinctly pointed out by De Saussure (Voyages, §§ 974-978); their true origin was subsequently indicated by Messrs. Studer (1844) and Guyot (1847); and the excellent account of
- ↑ See General Map.
- ↑ I am indebted for this fact to Professor Gastaldi.
- ↑ Revue des Deux Mondes.
