260 ISOTHERMAL LINES. SECT. XXVI. 



St. George's Bay, Newfoundland, latitude 48 : and 

 lastly, the line of 32, the freezing point of water, passes 

 between Ulea in Lapland, latitude 66, and Table Bay, 

 on the coast of Labrador, latitude 54. 



Thus it appears that the isothermal lines, which are 

 nearly parallel to the equator for about 22, afterward 

 deviate more and more. From the observations of Sir 

 Charles Giesecke in Greenland, of Captain Scoresby in 

 the Arctic Seas, and also from those of Sir Edward 

 Parry and Sir John Franklin, it is found that the iso- 

 thermal lines of Europe and America entirely separate 

 in the high latitudes, and surround two poles of max- 

 imum cold, one in America and the other in the north 

 of Asia, neither of which coincides with the pole of the 

 earth's rotation. These poles are both situate in about 

 the 80th parallel of north latitude. The transatlantic 

 pole is in the 100th degree of west longitude, about 

 5 to the north of Sir Graham Moore's Bay, in the 

 Polar Seas ; and the Asiatic pole is in the 95th degree 

 of east longitude, a little to the north of the Bay of Tai- 

 mura, near the North-east Cape. According to the 

 estimation of Sir David Brewster, from the observations 

 of M. de Humboldt and Captains Parry and Scoresby, 

 the mean annual temperature of the Asiatic pole is 

 nearly 1 of Fahrenheit's thermometer, and that of the 

 transatlantic pole about 3^ below zero, whereas he sup- 

 poses the mean annual temperature of the pole of rota- 

 tion to be 4 or 5. It is believed that two correspond- 

 ing poles of maximum cold exist in the southern hemis- 

 phere, though observations are wanting to trace the 

 course of the southern isothermal lines with the same 

 accuracy as the northern. 



The isothermal lines, or such as pass through places 

 where the mean annual temperature of the air is the 

 same, do not always coincide with the isogeothermal 

 lines, which are those passing through places where the 

 mean temperature of the ground is the same. Sir 

 David Brewster, in discussing this subject, finds that 

 the isogeothermal lines are always parallel to the iso- 

 thermal lines ; consequently the same general formula 

 will serve to determine both, since the difference is a 

 constant quantity obtained by observation, and depend- 



