Page:Popular Science Monthly Volume 6.djvu/389

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glaciers prove a climate of intense and continued cold.

The cause of change in the sun's path he finds in changes in the distribution of the matter of the earth. He cites the fact of the earth's equatorial protuberance, and says the mass takes the form of an ellipse, and is not circular, as assumed by some mathematicians, and is itself a cause of change, altering the poles of rotation and the sun's path. Moreover, much may be due to former upheavals and depressions of the earth's crust. The increase of polar ice is, according to Mr. Belt, contemporaneous with increase of obliquity of the sun's path, and must diminish the difference between the earth's equatorial and polar diameters. The tendency of this would be to diminish the obliquity of the sun's path, ameliorate climate, and approximate to a uniformity of seasons and of day and night.

The coming of the cold climate, and consequent increase of polar ice, he thinks was gradual and continuous, and he finds no evidence in Scotland, or elsewhere, of interglacial periods of mild climate. Mr. Belt claims that the glaciation of the north and south poles was simultaneous, as the climate north and south of the equator must have been nearly the same.

This accumulation of ice at both poles accounts, in Mr. Belt's opinion, for several phenomena usually attributed to elevation of land. He thinks the level of the ocean must have been lowered not less than 2,000 feet to supply the ice-sheets.

In the ice once formed upon the polar regions, Mr. Belt finds a dynamic agent adequate to important geological changes. Thus their weight would cause the polar lands to sink until the earth attains its normal form; by their melting, and flowing toward the equator, the equilibrium is disturbed. But the disturbance from this cause is probably very small, "if," as Mr. Belt concludes, "the earth's interior be as cold as space, and movements occur only in its upper strata."


An Ornithological Land-lubber.—Toward the end of last December, the Challenger expedition visited Prince Edward's Islands, situated about 1,100 miles southeast of the Cape of Good Hope. We find in the Times the following notes concerning the habits of the albatross, a bird which frequents these islands in enormous numbers: "The whole of the wet, sodden, flat lands of Marion Island, one of the group, were studded with albatrosses, sitting on their nests. The magnificent birds, most of whom were asleep, covered the ground in such numbers that they looked like a flock of sheep scattered over a meadow. The nests were freshly covered with tufts of grass and moss, and stood some two feet above the swampy ground. It was evidently the beginning of the breeding-season, as few eggs were attainable. These splendid birds, weighing 19 ½ pounds, and measuring 10 ½ feet from tip to tip of wing, seen to such advantage while in their glory at sea, so evidently at home as they sweep gracefully through the air, are, on land, 'completely at sea.' It appears impossible for them to hover; so, on alighting at the end of a swoop, the momentum of the body continues after their feet have touched the ground, until they literally turn head-over-heels on to their backs, from which inglorious position their efforts to regain their equilibrium are any thing but graceful. While advancing to the nest, the neck is extended and the body lowered, as they waddle along, like a goose. To rise in the air, they are obliged to run, with extended wings, for some 200 yards, over the soaking grass, before they attain sufficient velocity for the air to get under their wings, and allow them to feel themselves again masters of the situation. Once landed, they are powerless to resist attack: a sharp snap of the beak is their only means of offense or defense. In taking their eggs, the readiest way is to push them backward with a stick forced against their breast, which, balanced as they were, on the edge of the raised nest, was easy work, the drop of two feet being just sufficient to send them on to their backs and prevent them rising, until after the prize was captured."


Decomposition of Eggs.—For some time before his death, Dr. Grace-Calvert was engaged, in company with Mr. William Thomson, in investigating the subject of the decomposition of eggs. From these researches,