26# M. Kupffer on Iso-geothermal Lines. 



ground is as 5°.2. It is the same at Paris and Kasan, where 

 the inclination differs little. At Paris the intensity is 1.348, 

 and the temperature of the ground 9°. 2, and at Kasan the one 

 is 1,320 and the other 5°. At TenerifFe the intensity is 1 .298, 

 and the temperature 14§°, whilst at Naples the one is 1.275 

 and the other 13°. 



We may hence easily understand why the pole of intensity 

 is to the south of the pole of inclination. As the temperature 

 of the ground goes on diminishing to the north, the lines of 

 equal inclination nearest the pole of inclination pass through 

 colder points to the north of this pole than to the south ; but 

 in these colder points, the intensity, according to the princi- 

 ples above laid down, ought to be weaker than in the others. 

 We ought, therefore, to seek for the pole of intensity, that is, 

 the point where the magnetic intensity is a maximum to the 

 south of the pole of inclination ; and it is actually there where 

 it is found by the calculation of the last observations of Mr 

 Hansteen. The pole of inclination is in 71° iat. and 102° 

 long. ; that of intensity is in 5G)° of Iat. and 80° of long, west 

 of Paris. 



Such is a very imperfect account of M. KupfFer's memoir, 

 as we find it in an abstract in the Bihl. Universelley where 

 the formula, with the numerical values of a and h, are unac- 

 countably omitted. 



It is obvious that M. Kupffer has not seen Dr Brewster's 

 paper on the mean temperature of the earth, where the same 

 results nearly, respecting the isothermal equator, are deduced, 

 which M. Kupffer deduces for the iso-geothermal equator. The 

 whole of M. Kupffer's valuable results present the most 

 striking confirmation of the isothermal law of Dr Bnewster, 

 communicated nearly ten years ago to the Royal Society of 

 Edinburgh, that the distribution of temperature on the earth's 

 surface is related to four poles of maximum cold, two to the 

 north, and two to the south of the equator, and nearly related 

 in position to the magnetic poles of the earth. 



We expect to be able in an early Number to give an ab- 

 stract of Dr Brewster's paper, accompanied with a map of the 

 isothermal lines surrounding the two poles of maximum cold 

 in the northern hemisphere. 



