2 Physical Changes upon the 'Moon's Surface . [January, 
The question of the present condition of the surface of 
the moon has engaged, therefore, the attention of some of 
the most eminent astronomers, and much has been done 
towards obtaining the information necessary for the proper 
consideration of the problem. But though much has been 
done in this direction, very much more remains to be done 
before this question can be held to admit of decisive settle- 
ment ; for though the general nature of the lunar formations 
and surface has been made out fairly well, the details, which 
are of the utmost importance, are only very partially under- 
stood. The paucity of material available on which astrono- 
mers in general may found an opinion is not widely 
understood, for, with the exception of a few pages in the 
great work of Beer and Madler’s “ Der Mond,” and a small 
work by another great selenographer (Schmidt, of Athens), 
also entitled “ Der Mond,” until lately no published informa- 
tion may be said to exist accessible to astronomers in 
general. Hitherto information, with regard to the details of 
the structure of the formations on the surface of the moon, 
has had to be obtained directly by the careful study of the 
lunar surface, — a work necessarily occupying years, and only 
to be acquired by assiduous labour. These particulars, though 
not at first sight of importance, must not, however, be over- 
looked, for it will subsequently appear that they go far to 
explain the position now occupied by the question — What 
is the present condition of the lunar surface ? 
It is a remarkable circumstance, in relation to this ques- 
tion, that whereas those astronomers who have devoted 
much time and labour to the study of the moon’s surface, 
and to whom astronomers in general are mainly indebted 
for our present knowledge of the surface of our satellite, 
hold in general one view as to the present condition of the 
lunar surface, astronomers as a body hold a very different 
opinion. To take a striking instance, — scarcely any astro- 
nomer known to have devoted time to the study of 
selenography doubts that many processes of actual lunar 
change are in progress, and it is doubtful if there is one 
who could not promptly instance one or more such cases. 
Yet the general opinion of astronomers appears to be 
against any such physical changes having occurred. And 
another instance, almost as striking, exists in connection 
with the subject of the lunar atmosphere : whilst all 
selenographers appear to have detected instances where the 
existence of this atmosphere is revealed, astronomers in 
general appear to question almost the possibility of its 
existence, and this in face of the absence of any evidence 
