i $73-] Changes in the Moon's Surface. 495 



lever du soleil a son horizon, cette profonde cratere, dans 

 le diametre est 5*6 milles Anglais, etait parfaitement 

 disparu ; seulement un lueur, un petite image blanchatre se 

 presentait au lieu de Linne. Auriez vous bien la bonte de 

 faire quelques observations sur cette localite." 



Passing over the earlier observations made in accordance 

 with this suggestion, I quote the statements made by Dr. 

 Huggins, in the " Monthly Notices of the Astronomical 

 Society" for June, 1867. He remarks that "on May n, 

 1S67, Linne had the appearance of an oval patch on the 

 darker background of the Mare Serenitatis. The character 

 of the surface of the white spot may be described as similar 

 in appearance to that of a cloud, for it presented no distinct 

 details, and remained undefined when the small neigh- 

 bouring craters were seen with great clearness. The 

 absence of any defined points upon which the eye can rest 

 is probably the reason that the boiling motion of our atmo- 

 sphere is perceived in a much more marked manner over 

 the white spot than on the adjoining sharply-defined parts 

 of the moon's surface. From this cause, Linne appeared 

 on several occasions as a mass of white cloud in motion, at 

 the same time that the craters near it were seen steadily 

 and with distinctness. This cloudy appearance arises pro- 

 bably from a peculiar partly reflective property of the 

 material of which Linne consists. Some other portions of 

 the moon's surface reflect light in an analogous manner. 

 . . . The shallow saucer-like form of Linne was not seen, 

 but I have detected it on other occasions. ... In the 

 centre nearly of Linne, but rather nearer to the western 

 margin, was seen the small crater. This object was well 

 defined in the telescope. The interior of the small crater 

 was in shadow, with the exception of a small part of 

 it towards the east. The margin of the small crater was 

 much brighter on the western side, and at this part appears 

 to be more elevated above the surface of Linne. Under 

 very oblique illumination, this high western wall appears as 

 a small brilliant eminence, and casts a shadow which 

 is somewhat pointed. ... I estimated the diameter of the 

 small crater to be rather greater than one-fourth of the 

 diameter of the white spot." .... On the evening of July 9, 

 the boundary of Linne was noticed not to end abruptly, 

 but to pass " gradually into the darker surface of the 

 Mare Serenitatis." 



Dr. Huggins then proceeds to inquire into some of 

 the historical evidence. " Herr Schmidt," he says, " is of 

 opinion that a great change has recently taken place in the 



