400 Messrs. De La Rue, Stewart, and Loewy [June 19, 



From these we derive the following values of a period of oscillation, 

 by taking the differences in dates between the positive extremes : — 



27 days, 21 days, 29 days, 30 days, 22 days. Mean, 25*8 days ; 

 while doing the same with the negative extremes, we obtain 



24 days, 22 days, 31 days, 17 days, 32 days. Mean, 25-2 days. 



5. The second of the three periods extends from the end of June to 

 the beginning of November 1860. Treating this in the same manner, 

 we obtain : — 



