Academy of Sciences in Paris. 385 



the polar ices, but, except in a few points, and during a very short 

 period of the year, their summer limits also. The north winds, the 

 force of which in the open plains is not moderated hy any chain of 

 mountains to the west of the meridian of the lake Baikal as far as 

 the 52nd degree of latitude, and to the west of the meridian of Bolor, 

 as far as the 40th degree, pass over a field of ice covered with 

 snow, which prolongs, as it were, the continent even to the pole ; on 

 the other side, Asia offers to the influence of the solar irradiation 

 but a very small portion of country situated under the torrid zone 

 between the meridians which bound its eastern and western extremi- 

 ties. The equator passes only through a few islands, Sumatra, 

 Borneo, Celebes, and Gilololo ; during the whole remainder of its 

 vast extent, the equinoctial line cuts only the ocean : whence it 

 results that the continental part of Asia under the temperate zone does 

 not enjoy the effect of ascending currents similar to those which the 

 position of Africa renders so advantageous to Euro'pe. There are 

 also other causes which tend to increase the frigidity of Asia ; these 

 are 1st, Its position with respect to Europe, which gives the latter 

 all the western coasts, always under the temperate zones, much 

 warmer than the eastern ones ; 2nd, The form of its outlines, which, 

 to the north of the parallel of 35, present neither gulfs nor peninsular 

 prolongations of any consequence ; 3d, The form of its surface, which 

 has, in one part, chains of mountains intercepting the approach of the 

 south winds over a great extent of country, and in another, a series 

 of high platforms lying in a direction from south-west to north-east, 

 which, accumulating and preserving snow even in the midst of sum- 

 mer, act, by means of descending currents, on the countries which 

 they bound or traverse, and thus lower their temperature. These 

 contrasts between Europe and Asia present a summary of the causes 

 which act simultaneously on the inflexions of the isothermal lines 

 between the different seasons, and which are particularly perceptible 

 to the east of the meridian of Petersburg!!, where the continent of 

 Europe joins Northern Asia in a width of 20 degrees of latitude. 

 The east of Europe and the whole of Asia, to the north of the 

 parallel of 35 degrees, have a climate eminently continental, as dis- 

 tinguished from the climate of the isles and the western coasts ; 

 they have, both from their form and their position with respect to 

 the west and south-west winds, a climate of excess analogous to 

 that of the United States of America, that is to say, very hot sum- 

 mers succeeding very severe winters. At Astracan M. de Hum- 

 boldt has seen grapes as fine and as ripe as in Italy or the Canaries ; 

 although in the same spot, and even much more to the south, at 

 Kislar, which is in the same latitude as Avignon, the thermometer 

 (Centigrade) often descends in winter 28 and 30 degrees below zero. 

 A more profound knowledge of the laws regulating the temperature 

 of the earth in Asia, may produce a modification of the ideas enter- 

 tained respecting the circumstances which have attended the last 

 terrestrial revolutions. Thus, when it was known that the bones of 



