ON GEOSBAPHT. 571 



describe a spiral, of which each coil is nearly horizontal, half of the spiral 

 being abo\'e the horizon, and half below ; the coils being much opener in the 

 middle than near either end. 



The climates, in the astronomical sense of the word, are determined by 

 the duration of the longest day in different parts of the earth's surface; but 

 this division is of no practical utility, nor does it furnish any criterion for 

 judging of the climate in a meteorological sense. 



The natural division of the surface of the globe is into sea and land: about 

 three fourths of the whole being occupied by water, although probably no 

 Avhere to a depth comparatively very considerable, at most of a few miles on 

 an average. The remaining fourth consists of land, elevated more or less 

 above the level of the sea, interspersed, in some parts, with smaller collec- 

 tions of water, at various heights, and, in a few instances, somewhat lower 

 than the general surface of the main ocean. Thus the Caspian sea is said to 

 be about 300 feet lower than the ocean, and in the interior part of Africa 

 there is probably a lake equally depressed. 



We cannot observe any general symmetry in this distribution of the earth's 

 surface, excepting that the two large continents, of Africa and South 

 America,-bave some slight resemblance in their forms, and that each of them 

 is terminated to the eastward by a collection of numerous islands. The large 

 cap^s projecting to the southward have also a similarity with respect to their 

 form, and the islands near them: to the west the continents are excavated 

 into large bays, and the islands are to the east: thus Cape Horn has the 

 Falkland Islands, the Cape of Good Hope IMadagascar, and Cape Comorin 

 Ceylon, to the east. (Plate XLII, XLIII.) 



The great continent, composed of Europe, Asia, and Africa, constitutes 

 about a seventh of the whole surface of the earth, America about a sixteenth, 

 and Australasia or New South Wales about a fiftieth; or, in hundredth 

 parts of the whole, Europe contains 2, Asia 7, Africa 6, America 6, and 

 Australasia 2, the remaining 77 being sea; although some authors assign 72 

 parts only out of 100 to the sea, and 2S to the land. These proportions nid.y 

 be ascertained with tolerable accuracy by weighing the paper made for cover- 



