ON GEOGRAPHY. 437 



'""and the tropics, he is vertical twice in the year, when his declination is equal 

 to the latitude of the place, and his least meridian altitudes, which are 

 unequal between themselves, are at the solstices. At the tropics, the 

 meridian sun is vertical once only in the year, and at the opposite solstice, 

 or the time of midwinter, his meridian altitude is 43 4', as with us in 

 April, and the beginning of September. At the polar circles, the sun 

 describes on midsummer day a complete circle, touching the north or south 

 point of the horizon ; and in midwinter he shows only half his disc above 

 it for a few minutes in the opposite point ; that is, neglecting the elevation 

 produced by refraction, which, in these climates especially, is by no means 

 inconsiderable. At either pole, the corresponding pole of the heaven being 

 vertical, the sun must annually describe a spiral, of which each coil is 

 nearly horizontal, half of the spiral being above 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 pro- 

 bably no where 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 collections of water, at various heights, and, in a few instances, 

 somewhat lower than the general surface of the main ocean. Thus tho 

 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, have some slight resemblance in their forms, and that each of 

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

 The large capes 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 Madagascar, 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 six- 

 teenth, 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 28 to the land. These pro- 

 portions may be ascertained with tolerable accuracy by weighing the paper 

 made for covering a globe, first entire, and then cut out according to the 

 terminations of the different countries : or, if still greater precision were 

 required, the greater part of the continents might be divided into known 

 portions of the whole spherical surface, and the remaining irregular por- 

 tions only weighed. 



