±96 Notices respecting New Books. 



just made, except as giving some idea of the large reduction 

 it would be advisable to make in Dr. Stoney's figures. The 

 lithosphere of course is not homogeneous, and alteration in the 

 bulk-modulus with the depth must almost certainly be gradual. 

 I would also point out that, whether one treats the earth 

 as possessed of uniform elasticity or not, data deduced from 

 uniform surface loading are hardly calculated to throw much 

 light on what happens when the loaded area is but a small 

 fraction of the surface. If the loaded area be only a few 

 hundred, or even thousand, square miles, a much better idea 

 of the order of magnitude of the elastic effects due to denuda- 

 tion or deposition would probably be obtained by an application 

 of Cerruti and Boussinesq^s results'* for a locally loaded 

 infinite plane. As to possible gradual — i. e. nonelastic and 

 viscous — results, elastic solid theory is but an imperfect guide. 

 April 6, 1899. CHARLES Chree. 



XLY. Notices respecting New Books. 



Matter, Energy, Force, and Work ; A Plain Presentation of Fun- 

 damental Physical Concepts and of the Vortex-Atom and other 

 Theories. By Silas TV. Holhax, Emeritus Professor of Physics 

 in the Massachusetts Institute of Technology. New York : The 

 Macmillan Company, 1898. 

 npHE aim of the author in writing this volume has been to present 

 ■*- the fundamental definitions and concepts of physics in a 

 logical order. Assuming the existence of space, he points out that 

 certain portions of it are possessed of the power to affect our senses 

 and other portions of space ; in such portions substance exists. 

 Substance is composed of matter, and its power to produce external 

 effects may be attributed to the energy of motion of its matter; 

 matter of itself having no properties except that it occupies space 

 and can possess kinetic energy. The concept of energy is thus 

 made more fundamental than that of force, which is defined as the 

 action of energy in producing a tendency to change of motion of 

 bodies. This treatment leads to the doctrine of the conservation 

 of energy and a discussion concerning the nature of the various 

 forms of energy, and is followed, in the second part of the volume, 

 by an account of the vortex-atom theory of matter. 



The author appears to us to have introduced an unnecessary 

 complication into his work by his respect for the term mass as 

 ordinarily used to indicate quantity of matter. The term has no 

 meaning until the method of estimating quantities of matter has 

 been agreed upon ; ordinarily, mass is measured by its capacity for 

 acquiring momentum under given velocity, because force and 

 momentum are regarded as more fundamental than energy ; it is, 



* See Todhunter & Pearson's l History,' vol. ii. part 2, arts. 1489 

 et seq., or Love's ' Elasticity, 3 vol. i. chapter 9, also Phil. Mag. March 

 1897, p. 173. 



