AND ITS DISTPaBUTION. 47 



dent on local circumstances than on the temperature of the 

 atmosphere. No doubt the latter has on the whole the most 

 determining influence; but yet, as Kupffer has already 

 remarked, the isogeothermal lines are not parallel in their 

 concave and convex inflections to the climatic isothermals 

 which are given by the mean atmospheric temperature. The 

 amount of rain, and the depth to which it penetrates, the 

 ascent of warm springs from depths, and the very various 

 conducting power of the soil,( 50 ) all appear to be particularly 

 influential. " At the northernmost point of Europe, in Pin- 

 mark en, in 70 and 71lat, there is no connected 'ground- 

 ice/ Proceeding eastward to the valley of the Obi, 

 we find the ground-ice at Obdorsk and Beresow 5 more 

 southerly than the North Cape. The cold of the ground 

 continues to increase as we advance eastward, with the ex- 

 ception of Tobolsk on the Irtish, where the temperature of 

 the ground is lower than at Witimsk in the valley of the 

 Lena, which is 1 more to the north. At Turuchansk 

 (65 54' lat.) the ground is still not frozen, but the limit 

 at which the ground-ice begins is very near. At Amginsk, 

 south-east of lakutzk, the ground is as cold as at Obdorsk, 

 5 further to the north ; so also at Oleminsk on the 

 Tenisei. Prom the Obi to the lenisei, the curve which 

 bounds the ground-ice appears to rise 2 of latitude more 

 towards the north; and then to re-descend, to cross the 

 valley of the Lena, almost 8 south of the parallel in which 

 it crosses the lenisei. Further to the east the line re-ascends 

 towards the north." ( 51 ) Kupffer, who has visited the mines 

 of Nertschinsk, has pointed out, that apart from the great 

 connected region of the ground-ice, the same phenomenon 

 occurs more to the south in detached patches, or as it were. 



