Notices respecting New Books. 141 



hensiveness of the geometrical relation which forms the mathematical 

 expression of this principle. But, independently of these characters, 

 which are inherent in the nature of the phenomena, and not liable 

 to modification in consequence of the greater or less power brought 

 to the study of them, the present book derives a special value and 

 beauty from the sagacity with which the author has followed out 

 the physical and mathematical consequences involved in the prin- 

 ciple of the equality in all directions of the tension of a liquid sur- 

 face, and in the resulting geometrical relation of the constancy of 

 the sum of the principal curvatures of such a surface, combined 

 with the completeness and accuracy of the experimental verification 

 of theoretical deductions which he has obtained. In fact, the judg- 

 ment and ingenuity shown in devising the methods of experiment, 

 and the skill with which they have been applied, have enabled the 

 author to trace out, with a minuteness that has not often been 

 equalled in other branches of Physics, the characteristics of the phe- 

 nomena under investigation. These phenomena also being compa- 

 ratively simple, in the sense of its being possible to isolate almost 

 completely by the methods adopted the effects of the particular 

 causes it was the author's object to stud} r , these researches form a 

 remarkable example of the close correspondence between theory 

 and experiment, worthy to be compared with Schwerd's memo- 

 rable work on the Phenouiena of Diffraction, a work with which 

 Professor Plateau's presents another point of analogy in the familiar, 

 every-day character of many of the phenomena with which it deals. 



Contributions to Selenoqraphij. By William Radcliff Birt, 

 F.R.A.S., F.M.S. ^ London : Taylor and Francis. 1874. 

 We are glad to see, by a copy of the above work which we have 

 received for review, that Mr. Birt has put together in one volume 

 his more recent labours connected with Selenography ; for not only 

 are there to be found among them able discussions of matters con- 

 nected very closely with interesting questions of present interest in 

 the science, but we are convinced, from a careful examination of 

 Mr. Birt's production, that it will prove of great value to every 

 s.udent of the lunar surface who may possess a copy — and that 

 not only because in future years it will be a work to which the ama- 

 teur may turn to compare his own observations with those there 

 recorded of some of the most minute of all lunar objects, in the full 

 confidence that they were carefully drawn and correctly described 

 for the epochs of observation, but because it is a volume likely to 

 be of essential service to every real student in connexion with his 

 own method and mode. Readers of the Beports of the British As- 

 sociation for the Advancement of Science will remember that in 

 1864 the Association voted a grant for the purpose of mapping the 

 surface of the moon, which was continued for three years — the re- 

 sult being that three areas of the contemplated map, on a scale of 

 200 inches to the moon's diameter, by Mr. Birt, with catalogues of 

 the objects, were published in the volumes for 1806 and 1868. The 

 first of Mr. Birt's contributions to Selenography, published hide- 



