146 HEAT OF LOWEST STEATTJM OF AIR. 



For the determination of the course of iso- 

 therms, for degrees of temperature below 5°CL 

 (41° Pahr.), we have as yet but very meagre 

 materials. They seem, however, to indicate that 

 the North Pole is not the coldest point of the 

 earth, but that there are in the northern hemi- 

 sphere two points of greatest cold. According to 

 Kaemtz, one lies in Siberia, about the promontory 

 of Taimura, near the northernmost point of Asia, 

 and the other to the north of Barrow's Straits, 

 at the extremity of Baffin's Bay. 



The lowest annual means which have been 

 hitherto found, at least from observations con- 

 tinued for at least one year, are the following : 



At Ustyansk, a small town at the mouth of 

 the Yana, in Siberia, in the same latitude as the 

 North Cape of Europe, -16° C. (2°-5 Fahr.) 



At "Winter Harbour, Melville Island, in 

 lat. 74°-8'N.,— 18°'7C. (l°-75 F.) 



At the island of Igloolik, at the north of 

 Hudson's Bay, in lat. 69°'3' N.,— 16°-6 C. 

 (l°-7 P.) 



While, therefore, in great deep lakes, the influence of a 

 temperature of 4° reaches to the lowest depths, and does 

 not permit the bottom to be cooled below that point, the 

 winter-cold, which cannot be transmitted downwards 

 except by conduction, can penetrate to but a slight depth. 



