OUGHT OF ERUPTIVE AND PRIMARY ROCKS. 335 



from 1821 to 1830, had been experienced in that part of Europe 



lying north of the Alps, 21 had occurred in summer, 34 in 



autumn, 43 in winter., and 17 in spring. In the same way Merian 



arranged all the earthquakes, which had been observed in Basle 



up to the end of 1836., with the following results: 



Summer 18. 



Autumn 39. 



Winter 41. 



Spring 22. 



The most important statistics of this character have however 

 been furnished by Perrey of Dijon, who seems to have given special 

 consideration to this subject. He has classified, according to the 

 •seasons of the year, 2,979 earthquakes, which have taken place in 

 Europe and the immediately adjoining parts of Africa and Asia 

 from the year 306 to the year 1844, and f'ouad: 

 653 to have taken place in summer 

 705 *' autumn 



<91 1 u winter 



710 u spring 



The maximum falls in the coldest and the minimum in the 

 •warmest season of the year, while in spring and autumn the num- 

 bers are almost equal. Naumann considers that these observations 

 almost conclusively prove that " at least in Europe and the coun- 

 tries immediately bordering on it, autumn and winter must 

 *' be regarded as the seasons, in which earthquakes most frequent- 

 " ly occur." He adds that it is difficult to find a satisfactory expla- 

 nation of this fact, that the cause ought perhaps to be sought for 

 more in eosmical than in meteorological relations, and finally asks 

 *' May not the position of the earth in the winter, ie. in the perihe- 

 lion exercise an influence ?"* This question he leaves unanswered 

 contenting himself with declaring that the mere difference of tem- 

 perature in the seasons of the year can not explain the matter- 

 If, as is supposed in the first part of this paper, there exists in the 

 interior of the crust a central metallic globe surrounded by a fluid 

 -zone, it is quite reasonable to suppose that the former may be influ- 

 enced by the heavenly bodies, that it is attracted by the sun and 

 moon and that the attraction exerted is the more powerful the nearer 

 these bodies approach the earth. Sinee the sun is nearest 

 to the earth in the winter, there would appear to be grounds 

 ifor attributing earthquakes partly to the attraction exercised 



* LeMouch, I, 213. 



