252 M. KupfFer on Isogeothermal Lines. 



thermal lines are always parallel to the Iso-geothermal ones. 

 Hence the general formulae which Dr Brewster has given for 

 the points of the isothermal lines in all latitudes and meridians, 

 are applicable to the points of the iso-geothermal lines by ad- 

 ding or subtracting a quantity depending on the distance of 

 the place from the neutral isothermal line, — a quantity which 

 can be determined only from a numerous series of observa- 

 tions. 



In a valuable paper, of which we propose to give a short ac- 

 count, entitled, On the Mean Temperature of the air and of 

 the ground in some parts of Eastern Russia, which was read 

 to the Academy of St Petersburg on the 18th February 1829, 

 M. KupfFer has projected the iso-geothermal lines as formed 

 by the temperatures of springs in different places, and he con- 

 cludes that the iso-geothermal lines are far from coinciding 

 with the isothermal lines. This result stands in direct oppo- 

 sition to that obtained by Dr Brewster, and therefore requires 

 some examination. 



From the sketch of the iso-geothermal lines and the isother- 

 mal ones, as given by M. Kupffer, it is obvious that, as they ap- 

 proach to the Arctic regions, all approximation to parallelism 

 disappears. But this arises from the imperfection of the iso- 

 thermal projection as given by Humboldt, who was not posses- 

 sed of sufficiently numerous observations to give them more cor- 

 rectly. In the formulae of Dr Brewster, verified by the accu- 

 rate observations of Sir Charles Giesecke in Greenland, and of 

 Mr Scoresby in the Arctic Seas, and still more strikingly con- 

 firmed by the subsequent observations made in the voyages of 

 Sir Edward Parry and Sir John Franklin, the isothermal lines 

 in Europe and America quit one another entirely and surround 

 two cold poles, one in America and another in the North of 

 Asia. Now it is a most remarkable fact, that the American 

 and European portions of M. Kupffer's iso-geothermal line of 

 0° Reaumur, actually separate, and are clearly going round 

 the two poles of maximum cold. This valuable result not 

 only removes every difficulty respecting the apparent want of 

 parallelism of the two classes of lines in the Arctic region, 

 but it affords an independent proof of the general correctness 



