DEPTH OF PERMANENTLY FROZEN SOIL IN THE POLAR REGIONS. 273 



places, the ground is either covered with thick moss or shaded by brush- 

 wood, and its surface temperature in the hottest day is not likely to ex- 

 ceed 70° F., whereas earth exposed to the rays of the sun may easily 

 reach a temperatui-e of 120° F.' Fort Rae is situated on a long arm or 

 inlet of Great Slave, having a depth of 10 or 12 feet of water. 



7. Lat. 62°, long. 129° 40'.— Jakutsk, Siberia.— The great depth of 

 permanently frozen soil in this part of the valley of the Lena has long 

 been well known ; but the following extract translated from a recent 

 paper by Doctor Alex. Woeikof, of St. Petersburg, entitled ' Klima von 

 Ost-Siberien,' contains information on the influence of local conditions 

 which will make it of value to observers, and we therefore reproduce it. 



' The further north,' he remarks, ' the longer is the duration of cold 

 in valleys in comparison with that on higher ground. The effect extends 

 to a part of autumn and spring, and is observable in the mean tempera- 

 ture of the year.' 



The following observations of earth temperatures are a proof : — 



Thus, on heights in the vicinity of Jakutsk the earth temperature is 

 from 8*1° to 8-6° F. higher than it is in the town and valley at the same 

 depth, and it is even lower at 300 feet in the former than at 50 feet in 

 the latter locality. The total depth of frozen soil is, according to Midden- 

 dorf," more than twice as great in the valley as it is on the heights ; and 

 observe that these lesser heights are in winter relatively colder than 

 higher isolated mountains. Middendorf also states that no frozen soil was 

 found at 60 metres above the level of the river at the mouth of the Maja, 

 in Aldan, but that it was found about four miles and a quarter up the 

 stream at three metres above the level of the river, and that about 28 

 miles further, in the mountains, there is a deep hollow from which 

 aqueous vapour is constantly rising. 



Knppfer asserts that in Bergrivier Nertschinsk, in the Trech S wjatitilei 

 mine, frozen soil was found at a depth of 174 feet, but that in Woss- 

 dwischenst mine, which lies 230 feet higher, the frozen soil ceased at 50 

 feet. Even in Altai it is acknowledged that many valleys are colder than 

 the neighbouring heights. 



Dr. Woeikof sums up a number of observations in the following 

 sentences, which apply to the greater part of East Siberia, but more 

 particularly to the north-east portion : — 



(1) As the greater cold coincides with calms and light winds, the 

 valleys and lower grounds are colder than the heights. 



(2) The temperature of isolated mountains is relatively higher than 

 that of lesser elevations. 



(3) The lowering of temperature in the valleys is so lasting and 

 considerable that the mean of the year is also lowered, as is proved by 

 the observations of earth temperature. 



(4) The depth of the frozen soil is greater in valleys than on the 

 neighbouring heights, probably also than it is on the higher mountains. 



(5) In the Tundras of the far north (answering to the Barren grounds 



' M. Scher^'s shaft. " Sihirische Iteise, Bd, i. 



1886. T 



