104 



THE GEOLOGIST. 



19. Spirifera minima, Moore. Perfect enlarged exterior. 



20. . Exterior of the ventral valve. 



21. Terebratula (?) minvM, Moore. Perfect shell, enlarged exterior. 



22. . Interior of dorsal valve. 



23. Rhynchonella (?) coronata, Moore. Enlarged dorsal aspect. 



24 . . Interior, showing ventral aspect. 



25. — — . Exterior of ventral valve. 



FOREIGN CORRESPONDENCE. 



Lunar relations of 'Earthquakes. 



M. A. Pekrey, in a paper read before the French Academy on the fre- 

 quency of earthquakes during the latter half of the 18th century — rela- 

 tively to the age of the moon,and of the frequency of the phenomenon at 

 the time of the moon crossing the meridian — furnishes a series of facts 

 worthy of the highest consideration. Referring to his previous labours 

 on this subject, he points out that, in the present paper, in contradis- 

 tinction to his former method, if an earthquake has taken place on the 

 same lunar day, in different parts of the earth without the intermediate 

 district being affected, that day is entered as many times as earth- 

 quakes have taken place. In this way he has found that from 1801 

 to 1850 the earth has trembled three thousand six hundred and fifty- 

 five days, with a marked preponderance at the syzygies. 



If the mean lunation of 29'53 days be divided into eight equal 

 parts the earthquakes will not be found to distribute themselves 

 equally, but will show a preponderence at the beginning, the middle, 

 and the end — the curves representing which will take a wave-like 

 form, with two maxima and two minima. 



Uniting the numbers of the first and last eighths of the lunar 

 month, the sum will express the monthly frequency at the new moon; 

 the second and third combined give the frequency during the first 

 quarter ; the fourth and fifth at the full moon ; while the sixth and 

 seventh show the frequency at the last quarter. 



Again combining the results for the two syzygies and the two 

 quadratures, we find that from 1751 to 1800 



Shocks of Earthquakes. 



At the Syzygies 190P18 



At the Quadratures 1753'82 



Difference in favour of Syzygies 14 7" 36 



After some further references to his preceding memoirs, M. Perrey 

 proceeds — " One is then justified in admitting that earthquakes are 

 more frequent at the syzygies than at the quadratures; the conclusion 

 we have arrived at from our researches of 1853 is now proved to be 



