Temperature of the Globe. 341 



the doctrine of the distribution of magnetism on the earth could 

 not be expected to make any important progress. Supported by 

 analogy, it has been attempted to simplify by a careful employ, 

 ment of well ascertained facts, the complicated doctrine of the 

 distribution of heat. Places having an equal mean temperature 

 of the year, of summer, or of winter, have been connected with 

 one another by curves. This was the origin of the system of 

 isothermal lines*, of which I published a full account in the 

 year 1817. They descend towards the equator, because in 

 Eastern Asia and the eastern parts of North America we find, 

 on an equal level above the sea, and in a more southern lati- 

 tude, the same temperature which we meet with in the centre 

 of Europe, in a more northern latitude. The remarkable cir- 

 cumstance, that the highest civilization of the species to which 

 we belong has developed itself, almost under the same latitudes 

 in the temperate zone upon two opposite coasts, the eastern 

 coast of the new and the western of the old continent, must 

 early call our attention to the difference of heat under the same 

 latitudes. The question arose by how many thermometrical de- 

 grees the old world was warmer than the new, and it is not 

 long since it was known, that the isothermal lines from the la- 

 titude of Florida to that of Labrador, do not run parallel, and 

 that the eastern and western coasts of North America are al- 

 most as different from one another as those of Western Eu- 

 rope and of Eastern Asia. The shape and grouping of 

 the continents, ^nd their relation to the neighbouring, seas, 

 are the principal causes which determine the inflection of the 

 isothermal lines, or the direction of equally warm zones, into 

 which we may conceive the whole globe to be divided. The 

 predominance of west winds in the temperate and cold re- 

 gions determines the difference of climates on the eastern and 

 western coasts of one and the same conUnent. The western 

 winds, which are considered as reactions of the tropical trade- 

 winds reach an eastern coast, after having traversed in winter 

 a continent covered with snow and ice ; to the western coasts, 

 on the contrary (in Europe as well as in New California and 



* De la Distribution de la Chaleur sur le Globe.— Mem. de U Soci^t^ 

 d'Arcueil, t. iiL » 



JANUARY — MARCH 1828. » 



