280 



METEOEOLOGY IN EUSSIA. 



nieroiivS bays aucl sounds north of America are covered with an un- 

 broken sheet of ice and snow. These bodies being very bad conduct- 

 ors of heat, their surface, and the air immediately overlying them, can 

 cool to a great extent, as would a continent. These facts should be borne 

 in mind wheu speaking of the climate of Eastern Asia and America, ex- 

 plaining the differences found, contrary to the general opinion of the 

 similarity of the eastern shores of both great continents. The changes 

 of temperature with elevation are also very much modified by the gen- 

 eral features of Eastern Siberia, geographically and climatically. We 

 know two high points of this country which have a higher mean winter 

 temperature than the surrounding lowlands. These points are Mount 

 Alibert 52^ 30' N. latitude, and 100° 41' longitude E. of Greenwich, 

 7.300 feet high, and the mines of Wosnesensk, 58° 46' latitude X., llo*^ 

 10' E., 2,817 feet high. (^) Igivehere the temperatures of January as they 

 were observed, and the supposed temperatures of the same points at sea- 

 level, according to Dove's isothermal map. 



Temperature, of January. 



We see that these high points have a much warmer winter tempera- 

 ture than was supposed. Wosnesensk is not very far from Jakutsk, 

 where the temperature of January is — 41° 4', that is, more than 27° lower. 

 Irkutsk is not far from Mount Alibert, and has a much lower winter 

 temperature. 



The increase with the height iu winter in these two cases being shown, 

 the question follows as to the cause. In clear, cold spring niglits vegeta- 

 bles are often known to suffer from frost in low situations, while those 

 on hills escape injury. This has long been explained by the action of 

 radiation and gravity, when the air is calm. The colder and denser 

 l)ortions have a natural tendency to flow downward, and this tendency 

 in a clear, calm night is not counteracted by the suu and winds, as it 

 is generally during the day. Now a condition, analogous to that of 

 spring, does prevail very generally iu Eastern Siberia, especially in 

 winter. The air is calm, the sky clear, the sun appears only for a short 

 time, and the superposition of strata of air which would be caused by 

 radiation and gravity is very little impeded. It is not to be wondered 

 at, then, that a condition which is rare in Europe and the United States 

 should be so common in Siberia, so as to raise even the mean tempera- 

 ture of high stations above that of low ones. A very general and strong 



(') For fnrtber particnlars see " Zeitschrift der Osterreichischen Gesellschaft fiir 

 Meteorologie," year 1871, p. 52. 



