CLIMATE. 151 



get as far north as the tropics, this differencee becomes very sen- 

 sible, and it has been truly observed, that the torrid zone may be 

 divided in three, viz : the equatorial belt, extending 10 or 15 de- 

 grees from the equator, and the two belts north, and south, be- 

 tween this and the tropics. The equatorial belt, properly so called, 

 is te mperate compared with the two others, the zone of the tropic 

 of Cancer being the hottest and least habitable part of the globe. 

 The greatest natural heat of which we are aware, has been ob- 

 served at Bagdad, at 33 degrees of N. lat, being 111 Fahrenheit. 

 There are many reasons why the equatorial belt should have a 

 uniform and somewhat mild temperature ; the clouds, the great 

 rains, the nights naturally cool and equal in length to the days, 

 and the great evaporations. As we go farther from the equator 

 the difference between the summer and winter temperature be- 

 comes more marked, the summers being, on account of the pro- 

 tracted heat of the day, very warm even in high latitudes, and the 

 winters extremely cold. Thus, even as far from the equator as 

 the 65th parallel of latitude, the power of the solar beams accu- 

 mulating through the long days, produces an effect which might 

 be expected only in the torrid zone. There have been examples 

 of forests having been set on fire, and of the pitch melting on the 

 sides of ships. Notwithstanding the general law of the decrease of 

 mean temperature as we recede from the equator, yet it is impos- 

 sible to draw any conclusion as to the climatic relations of a place 

 from its geographical latitude. If the earth's surface was entirely 

 homogeneous, either covered by water, or by land, possessing 

 the same capacity for heat, then the geographical latitude of a 

 place would determine its climate, and all places having the same 

 latitude would have a similar climate. This however, is not the 

 case, for although the local temperature of a country depends 

 very much upon its latitude, yet the nature of its surface, the 

 proportion of humidity, the distance from the sea, or from lakes 

 or mountains, and its elevation above the ocean, and the nature 

 of the prevailing winds, all have a share in determining the cli- 

 mate. The decrease of heat as we recede from the equator fol- 

 lows different laws in the two hemispheres, being greater in the 

 southern than in the northern, and is also affected by the longi- 



