Geological Society. 371 



historical account of the work of other theorists is appended ; and 

 the last chapter is devoted to the inequalities in the moon's motion, 

 arising from the action of the planets, the figure of the earth, and 

 the motion of the ecliptic. Comparative tables of notation, which 

 will certainly be found useful, together with an index complete 

 the volume. 



The peculiar difficulties of the Lunar Theory arise mainly from 

 the fact that the original investigators have generally confined 

 themselves strictly to their own methods, and this independence of 

 thought among the classical theorists may be fairly said to warrant 

 Prof. Brown in his peculiar treatment of the subject. Neverthe- 

 less, while in our present state of knowledge he does well in 

 recognizing the importance of some acquaintance with the older 

 methods and the necessity for a separate treatment for each in 

 order to show the relations which exist between them, the subject 

 cannot be considered to be in a perfectly satisfactory state until a 

 single uniform mode of treatment becomes possible without loss of 

 rigour or completeness. There can be no doubt that the time for 

 this will be hastened by Prof. Brown's work. A highly commend- 

 able feature of the book consists in the ample references, which 

 will enable the reader to continue his study of the more recent 

 theoretical investigations. It was of course impossible to include 

 all of these developments, and the author has shown excellent 

 judgment in his selection. If the work of Professor Grylden is 

 passed over almost without remark, this course is probably justified 

 by practical considerations of expediency, although it is to be 

 regretted that his work is not better known in this country. The 

 question of convergence being as it is of the utmost importance 

 for the legitimate use of infinite series, has scarcely sufficient stress 

 laid on it, although the absence of certain knowledge is a plausible 

 excuse. The remarkable contributions of Cauchy to this subject 

 might, however, with great advantage have been considered. But 

 with this single exception, we have nothing but praise for the 

 manner in which Prof. Brown has carried out his task, and we 

 recognize his book as a most important and valuable contribution 

 to a highly interesting branch of mathematics. It should be 

 mentioned that the volume in the matter of type and general 

 arrangement is quite up to the high standard we have learnt to 

 expect in books published under university auspices, and this fact 

 serves no small part in the lucidity of the explanations. 



W. E. Plummer. 



XXXVIII. Proceedings of Learned Societies. 



GEOLOGICAL SOCIETY. 



[Continued from p. 287.] 



May 27th (con.). — Dr. Henry Hicks, F.R.S., President, 

 in the Chair. 



2. ' The Linyula-Flsigs and Igneous Rocks of the Neighbourhood 



