Page:The fairy tales of science.djvu/360

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312
THE WONDERFUL LAMP.

each direction would be performed in about twelve hours, stoppages included.

The circumference of the earth measures 25,000 miles; if it were begirt with an iron railway, such a train as above described, carrying 240 passengers, would be drawn round it by the combustion of about thirty tons of coke, and the circuit would be accomplished in five weeks.

In the drainage of the Cornish mines, a bushel of coals usually raises 40,000 tons of water afoot high; but it has, on some occasions, raised 60,000 tons of water the same height. Let us take its labour at 50,000 tons raised one foot high. A horse worked in a fast stage-coach pulls against an average resistance of about a quarter of a hundred weight. Against this he is able to work at the usual speed through about eight miles daily; his work is therefore equivalent to 1000 tons raised one foot. A bushel of coals, consequently, as used in Cornwall, performs as much labour as a day's work of fifty such horses.

The Great Pyramid of Egypt stands upon a base measuring 700 feet each way, and is 500 feet high, its weight being 12,760 millions of pounds. Herodotus states that in constructing it 100,000 men were constantly employed twenty years. The materials of this Pyramid would be raised from the ground to their present position by the combustion of about 480 tons of coal.

The Menai Bridge consists of about 2000 tons of iron, and its height above the level of the water