66 Analyses of Books. [Jan. 



much lower than in other places under the same latitude. 

 With the fourth magnetic pole in the Indian Sea, we 

 require the observation that there is in its neighbourhood 

 no other land in a more southerly latitude than 30°. This 

 idea of a connexion between the earth's magnetism and its 

 temperature, has been taken up by Sir David Brewster ; 

 and in a copy of Hansteen's magnetic chart published by 

 him in his journal, he has laid down two frigid poles in the 

 northern hemisphere, the one in North America, the other 

 to the North of Siberia. It may be asked, what is the cause 

 of the low temperature at these points, and why does the 

 magnetic pole change its condition ? The principle cause 

 appears to be that the greater magnetic intensity, the inferior 

 temperature, and the aurora borealis proceed from a peculiar 

 dynamic influence in the internal parts of the earth, which 

 is yet unknown to us. If we had observations on the annual 

 mean temperature for 200 years in different parts of the 

 earth, especially in the greater geographical latitudes, we 

 should possess data to determine whether or not the altera- 

 tions in the magnetic pole produced a change in climate, 

 and also if such a connexion does exist between these 

 phenomena. 



It is remarkable that in 1825, although Hansteen had 

 previously paid great attention to the subject of the earth's 

 magnetic intensity, he had no knowledge of a system fur- 

 ther than that the intensity is greater at the poles than at 

 the equator. In 1830, he sketched out the system upon a 

 small part of the earth's surface, and in the same year com- 

 pleted his chart so far as observations allowed. Such is 

 the consequence of the combination of men of power and 

 cultivators of science. 



Article XII. 



ANALYSES OF BOOKS. 



Traite experimental de Electricite, et du Magnetisme, et de 

 leurs rapports avec les Phenomenes Naturels. Par M. 

 Becquerel, torn. i. Paris, 1834. 



This is an interesting work, and forms a concise digest of the facts 

 which have been ascertained in the important branch of science of 

 which it treats. 



