OF THE 



UNIVERSITY 



OF 



A COMPARISON OF THE FEATURES OF 

 THE EARTH AND THE MOON. 



BY N. S. SHALER. 



PRELIMINARY NOTE. 



The object of this paper is to set forth the general results of certain 

 studies concerning the form and structure of the lunar surface with reference to 

 various terrestrial problems. 



These studies were begun in 1867 with the Mertz equatorial of the Harvard 

 College Observatory, at the time when my lamented friend and colleague, Joseph 

 Winlock, was director, and have been continued in a desultory manner, from time 

 to time, for a third of a century. Between 1867 and 1872 about one hundred 

 nights were devoted to telescopic work ; since that time what has been done has 

 been almost altogether by means of photographs, which have of recent years 

 become much more convenient and for my purpose more serviceable than the 

 opportunities afforded by an instrument even if it were as good as the Harvard 

 Mertz. 



It should be observed that so far as possible my task has been kept apart 

 from problems of selenology or selenography strictly so called. The ends sought 

 have been those alone which had distinct reference to geology. Certain ques- 

 tions, as, for instance, that concerning the antiquity of the lunar surface, necessa- 

 rily touch upon matters which relate to the history of the moon as an individual 

 sphere. In fact almost all the questions brought up by studies on the satellite 

 are more or less entangled with those relating to the evolution of the planet, so 

 that except for the detailed account of the features of either body they must needs 

 be considered together. These features may be compared by types, and in the 

 main the following essay consists of such comparisons. 



If other duties permit I hope to present the matters discussed in the follow- 

 ing pages in a more extended form, one in which it will be possible to illustrate 

 the facts here set forth, as well as to discuss the conclusions attained in an ampler 

 manner. Almost all the points I have endeavored to make clear demand this 



