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GLACIER-EROSION THEORY

infinitely greater importance than the valleys either to the north orsouth of the Alps ; but they were never connected with a lake.

The question then arose, What was the physical reason of this greatdifference between the tropical mountains and those of temperateEurope ? Nearly thirty years ago, he was for ten or twelve yearsrambling about the Himalayahs along a stretch of 800 miles, and heused to open a map before him, and try to make out the comparativefeatures of European and Eastern mountains. lie looked to thenumerous lakes to the north and south of the Alps ; and he would putthe map of India alongside, where the same kind of rivers were de-bouching into the plains, but where there was an utter absence of lakesin connection with them; and he used to puzzle himself in trying todiscover a physical explanation of this difference. lie was perfectlysatisfied there must be some secondary conditions which were notcommon to the two, and he determined that, on his return to Europe ,he should make them the subject of special research; for at that timethe glacial investigations of Charpentier and Agassiz in the Alps wereunknown to a solitary wanderer in the Himalayahs. That intention hehad carried out, by repeated visits to the Italian valleys of the Alps .There was the same kind of elevation above the level of the sea, thesame kind of valleys, the same kind of fssures intersecting the greatridges—What then was the explanation ? This he would endeavourto indicate. About two years ago, March 5, 1802, as his friend SirRoderick Murchison was aware, a paper was brought before the Geo-logical Society of London by Professor Ramsay, which excited a greatdeal of attention, and gave rise to a very animated discussion. 'Thetheory of the paper was that, as a rule, lakes in all the temperate andcold regions of the world were the product of glacial excavation ; thatis to say, that wherever a glacier descended from a high ridge of moun-tains into a plain, it ploughed its way down into the solid rocks andcarved out a great lake. This was the theory, or rather hypothesiswhich Professor Ramsay put forward, to explain the lakes which wereso abundant in the valleys of the Alps . A similar speculation, butgreatly more restricted, had been advanced by Mortillet a short timebefore. He limited the action of the glacier to scouring out the silt ofthe filled-up lake basins, the origin of which he attributed to antecedentfissures the result of vpheavement. An application of this theory wasmade to the different physical phenomena which were connected withthe case; and it occurred to himself and many others (and he believedSir Roderick had an opinion in common with himself), that it was notadequate to explain the phenomena; and on the occasion when it wasproduced, he met it with the most lively opposition in connection withbis own experience in the Himalayan Mountains . The oppositionwhich he gave to it was upon these grounds. Many of them wouldremember that the lakes Maggiore and Como were upon the edge of theplains of Italy; that the glaciers, say that of the Ticino which camedown into the Lago Maggiore , descended along a steep incline, andwere at last delivered into that lake, which was about fifty miles long,and only eight or niue miles wide at its widest point. Its prolongationnearest to the Mediterranean attained a depth of about 2,GOO feet belowthe level of the sea. Where the river escaped out of the lake it wasnot more than about 600 feet above the level of the sea. It was a