Notices respecting New Books. 225 



ice melts : in either case the 0° C. is restored. Ultimately 

 the solid particles of the anhydrous colloid must lie side by 

 side with the ice particles, as they do when the two are mixed 

 as powders, as in § 162. They are as independent of one 

 another as are the particles of ether and chloroform when the 

 two are mixed, or as are the particles of two gases which 

 diffuse through one another without combination. 



I reserve the results which I have obtained with inorganic 

 colloids for a future communication. 



. The figure shows the same constants as were shown in the 

 figure, Paper IV., but with the new salts. 



XXIX. Notices respecting New Books. 

 The Moon, and the Condition and Configurations of its Surface. By 



Edmuxd Neiso^", F.B.A.S. 4'c. London: Longmans, Green, & Co. 

 TV/TANY distinct branches of observational astronomy have been 

 ■*•"•*- cultivated of late years, some to a much greater extent than 

 others; that which has received the smallest amount of attention 

 is Selenography, especially the topography of our satellite or the 

 configurations of its surface. It is true a few energetic workers 

 have been engaged for some years past in studying certain portions 

 of the lunar disk ; still the progress of selenography has been slow 

 as compared with that of other departments of astronomy. The 

 work now before us, if we are not greatly mistaken, will have an 

 opposite influence on the progress of the study of the moon's sur- 

 face to that which Madler's great work produced in his day ; for, 

 the opinion which prevailed (alluded to by our author) being that 

 the moon was an airless, waterless, lifeless, unchangeable desert, 

 astronomers then directed their attention to other fields of research, 

 and selenography rested on its laurels, making no further progress 

 for many years. 



The author has divided his work into two portions, the first of 

 which consists of five chapters, in which he treats (1) of the 

 motions, figure, and dimensions of the moon, (2) of the physical 

 condition of its surface, (3) of the lunar formations, (4) of lunar 

 history, and (5) of the variations of the surface. The greatest 

 portion of the materials of Chapter I. may be found in most astro- 

 nomical works ; the second chapter, however, treats at some length 

 on the much-disputed question of a lunar atmosphere, the author 

 considering that its existence must be regarded as certain. The 

 characteristics of the lunar surface, especially in connexion with 

 terrestrial analogies, are well treated in this chapter, as well as its 

 temperature as modified by the presence of an atmosphere. The 

 concluding paragraph of this chapter is important as bearing on 

 the analogy of lunar as compared with terrestrial forces. " The 

 gradual progress in our knowledge of the present condition of the 

 surface of our satellite is surely, if slowly, pointing out in unmis- 

 takable terms the entire analogy in nature, if not wholly in degree, 

 of the forces that have moulded the surfaces of the earth and moon 

 to their present state." 



Phil. Mag. S. 5. Vol. 2. No. 10. Sept. 1876. Q 



