EEYIEWS. 
417 
THE MOON * 
M K. proctor lias in this instance, we think, excelled his previous 
efforts, and has produced a book not only excellent in character and 
clear in style, but of a nature to command a large circulation, and to make 
selenography, from an unknown, an extremely popular pursuit. We know 
of no book in the whole literature of astronomy which deals so thoroughly 
with its subject, is so admirably .illustrated, and withal so clear in style, 
as this treatise on the moon. Although the earlier portions treating of the 
moon’s peculiar motions are difficult, yet the difficulty vanishes before even 
an unmathematical persevering student ; and the latter portion of the work 
is of a character so absorbingly interesting that it is difficult to lay down 
the treatise without finishing its perusal. We think that considerable 
credit is to be awarded to Mr. Proctor for his efforts to make the moon’s 
motions intelligible to the general student. He has spared no pains to 
make the subject completely clear, and he has given such a number of 
plates containing plans and diagrams, that we feel assured none will feel 
difficulty in completely understanding even the difficult questions he dis- 
cusses. But to our mind the most interesting portion of the work is 
that which relates to the general contour of the moon, and to the manner 
in which it has been produced ; as also to the important question whether 
there is volcanic action still going on in that portion of the orb which is. 
visible to us. Mr. Proctor gives all the views of those for and against the 
opinion that volcanic action is taking place, and he sums up as follows : — 
The only explanation available therefore appeared to be this — that a mass 
of matter had been poured into the crater from below, and had overflowed 
the barrier formed by the ring mountain, so as to cover the steep outer 
sides of the ring. Instead, therefore, of an outer declivity, which could 
throw a shadow^ there appeared to be an inclination, sloping so gradually 
that no shadow could be detected, the whole surface thus covered with 
eruptive matter shining with the same sort of light, so that a spot was seen 
somewhat lighter than the Sea of Serenity, and larger than the original 
crater.” To be sure this explanation may seem rather vague to the reader 
of this notice, who has not had the work before him, but it really is an._ 
admirably clear summary. However, it turns out that it has been shown 
by Browning in 1867 that Linn^ changes remarkably in aspect in a very 
fhort space of time, under changing solar illumination ; and the inference' 
would seem to be that the supposed changes have been merely optical.” It 
will be found that on every other part of the subject the author is as par- 
ticular in laying the arguments pro and con before his readers. Altogether 
Mr. Proctor has given us a book for which our most sincere thanks are due. 
And to him also, and Mr. Rutherford and the Rev. T. Webb, our grati- 
tude is owing for the magnificent atlas which accompanies Mr. Proctor’s 
book. This contains enlarged copies of Rutherford’s splendid photographs, 
* The Moon: her Motions, Aspect, Scenery, and Physical Condition.” 
By R. A. Proctor, B.A., Hon. Sec. R.A.S. London : Longmans, 1873. ‘-The 
Moon” (three photographs — several maps). By Rutherford and Proctor. 
Manchester: Brothers, 1873. 
VOL. XII. — NO. XLIX. 
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