56 Notices respecting New Boohs. 



a minimum, draws the two floating bodies together. The same 

 is true of case 3, provided the floating bodies are brought into 

 such proximity that a common bounding perimeter is pro- 

 duced by the interfering meniscuses. But when the proximity 

 is not sufficient to secure this condition, the disturbance of 

 equilibrium due to this interference results, as we have seen, 

 in the recession of the floating bodies. For in the latter case 

 the first effect of the interfering meniscuses (as previously 

 shown) is to augment the radius of curvature at the intersect- 

 ing portions; this is evidently equivalent to a tendency to 

 increase the bounding perimeter of the meniscuses enveloping 

 each of the bodies; so that the minimum principle operates to 

 separate them. 



Hence the two fundamental principles of capillarity — 1st, 

 that the elastic reaction is inversely proportional to the radius 

 of curvature of the meniscus, and 2nd, that the same contractile 

 reaction tends to reduce the perimeter to the smallest which 

 can be enclosed by its actual boundary, are coordinated, and 

 alike concur in furnishing complete explanations of this class 

 of phenomena, without the necessity of invoking the agency 

 of atmospheric pressure or the modifications of hydrostatic 

 pressure due to the operation of these molecular forces. 



Berkeley, California, October 10, 1882. 



IX. Notices respecting Neiv Books. 



Physics of the Earth's Crust. By Eev. Osmond Eisher. 

 London: Macmillan. (Pp. xiv-j-299.) 

 HPHIS work is not a mere reprint of papers well known to many 

 -*- of our readers, some of them having been printed in our 

 columns, though free use has been made of them. The author has 

 been " for many years past convinced that various questions of 

 Physical Geology might be answered negatively, if not positively, 

 by applying to them simple mathematical reasoning and quantita- 

 tive treatment." He candidly confesses that his views, " in some 

 respects, have been greatly altered by the application of this me- 

 thod." In evidence of this he expressly states that " the views now 

 put forward differ in some respects from those which I have pre- 

 viously published in contributions to scientific periodicals. But the 

 effect of the progressive application of the quantitative method 

 may be traced in the book itself ; and the development of ideas, 

 proposed in the earlier chapters, will sometimes be found to have 

 taken an unexpected turn later on. This remark applies especially 

 to certain hypotheses, which at first presented themselves in a 

 favourable light, to account for compression and for the formation 

 of ocean-basins." The same spirit is seen in what follows : — " On 

 a review of what I have writteu, I feel how many difficulties have 



