﻿relative to Lunar Activity. 189 



these spots/ Nos. 5 and 14 are also spots which were not 

 affected at the epoch of February and March 1870 ; and these 

 with No. 22 form, as it were, an outlying area to the locality of 

 group II. Spots Nos. 6 and 7 also form an additional area on 

 the east, so that the increase of visibility of the spots of group 

 III., viz. Nos. 22, 14, 5, 18, 9, 11, 6, and 7, occurred over an 

 area extending from the west to the east border of Plato. It is 

 remarkable that spots Nos. 17 and 10 did not increase in visi- 

 bility at this epoch, although situated on the area of group II. : 

 nor did No. 29 ; but this spot is situated near the north border.* 



In connexion with the third group, and especially with spot 

 No. 5, is a phenomenon of which mention should be made. In 

 the spring of 1870, some months after the maximum visibility 

 of No. 5 in August aud September 1869, a streak which had 

 not before been recorded was seen extending from No. 5 to- 

 wards No. 14 as a faint object. In December 1870 a streak 

 was observed on the opposite side or eastward of No. 5 ; the two 

 form an easy and at present somewhat bright object connecting 

 two arms of the " trident " 



From a careful consideration of the whole of the phenomena 

 presented during the twenty lunations, especially the three 

 groups of maxima at the epochs above stated, I am strongly dis- 

 posed to regard the agencies at present known capable of affect- 

 ing the appearances and visibility of lunar objects as perfectly 

 inadequate to produce the phenomena indicated by the curves. 

 The true nature of the agencies that have been instrumental in 

 their production can only be arrived at by long- continued obser- 

 vation. With a double length of curve, resulting from the ob- 

 servations of twenty additional lunations, we shall be better able 

 to determine if the curves of such neighbouring spots as Nos. 19, 

 13, and 22 will retain the features which are now so characteristic 

 of them — or that the inflections of the curves of Nos. 5 and 16 

 and of 22 and 7 will be continued, indicative of a physical con- 

 nexion of some kind between spots so widely separated as they 

 are. In the mean time, as the observations proceed these parti- 

 cular features may be confirmed, or new relations developed, 

 leading us onwards to a clearer view and a juster appreciation 

 of those forces which it is not impossible may yet be in operation 

 on the moon's surface. 



