arising from the drifting of heavy ice, I shall refer to Captain Scoresby's account of the tremendous concussion of fields. He observes that the occasional rapid motion of ice fields, attended with the destructive effects, which are produced on any opposing substance, exhibits one of the most striking, and, at the same time, one of the most terrific sights, which Greenland produces. These bodies not unfrequently acquire a rotary motion, by which their circumference attains a velocity of several miles an hour. If a field, thus in motion, comes in contact with another at rest, or more especially in n contrary direction of movement, the shock is dreadful. Some faint idea may, indeed, be conceived of the consequences which must ensue, when a body of more than ten thousand millions of tons in weight encounters resistance to its motion. The weaker field is crushed to atoms, with an awful noise; sometimes the destruction is mutual; pieces of huge dimensions, are not unfrequently piled to the height of twenty or thirty feet upon the top, whilst, doubtless, a proportionate quantity is depressed beneath. These stupendous effects, when viewed in safety, exhibit a picture sublimely grand; but where there is danger of being over-
- Captain Scoresby estimates that a field containing thirty nautical square miles in surface, with a thickness of thirteen feet, would weigh more than is here mentioned, allowing it to displace the water in which it floats to the depth of eleven feet. The weight would appear to be 10,182,857,142 tons, nearly in proportion of a cubic foot of sea water to sixty-four pounds.