Читать книгу Arctic Searching Expedition (Sir John Richardson) - comprehensive & illustrated - (Literary Thoughts Edition) онлайн

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In various parts of the lake, the gorges lying between the jutting bluffs of granite or slate are filled with deposits of sand rising in four or five successive terraces to the height of more than a hundred feet above the present surface of the water. Mr. Logan has measured some of the most remarkable, and Professor Agassiz devotes an interesting chapter to the discussion of their origin; in which he comes to the conclusion that they were formed by the waters of the lake itself, and have been raised, at various intervals, from the beach to their present levels, by the agency of the innumerable trap dikes, which cross the rocks in many directions.

Near Cape Choyyè, on the south side of Michipicoten Bay, a small gorge between two points of granite is filled, to the height of twenty-five feet above the water, with rolled stones and pebbles. These rounded stones vary in size from that of a hogshead to a hen's egg, and form a steeply shelving beach, with a flat terraced summit, the larger boulders being next the water, and the smaller pebbles highest up. As the cove is sheltered from high waves, the terrace could not be thrown up by the waters of the lake standing at their present height; nor can it be owing to the pressure of ice, since that would not graduate the pebbles.