The Garden Guide

Book: Gardening Science - Soils, Manure and the Environment
Chapter: Chapter 4: Weather and Climate

Extent of northern ice sheet

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1397. The northern ice extends during summer about 9ᆭ from the pole; the southern 18ᆭ or 20ᆭ; in some parts even 30ᆭ; and floating ice has occasionally been found in both hemispheres as far as 40ᆭ from the poles, and sometimes, as it has been said, even in latitude 41ᆭ or 42ᆭ. Between 54ᆭ and 60ᆭ south latitude, the snow lies on the ground, at the sea-side, throughout the summer. The line of perpetual congelation is three miles above the surface at the equator, where the mean heat is 84ᆭ; at Teneriffe, in latitude 28ᆭ, two miles; in the latitude of London, a little more than a mile; and in latitude 80ᆭ north, only 1250 feet. At the pole, according to the analogy deduced by Kirwan, from Mayer's Formula, and which is not however found to agree very exactly with what takes place, from a comparison of various observations, the mean temperature should be 31ᆭ. In London the mean temperature is 50ᆭ; at Rome and at Montpelier, a little more than 60ᆭ; in the island of Madeira, 70ᆭ; and in Jamaica, 80ᆭ.