670 SCIENCE PROGRESS 



from surreptitious sketches at a dinner of the Royal Society Club, the original 

 being in the print-room at the British Museum. 



The first chapter abounds with interesting biographical details of Cavendish. 

 The notes by Maxwell which are reprinted at the end of the volume contain 

 many pieces of work of peculiar value in electrostatic theory which are not 

 readily to be found elsewhere. The general impression derived from reading 

 the work is an admiration for the enormous care and accuracy of Cavendish 

 as an experimenter, and if an example might be quoted we would cite the 

 extraordinarily accurate determination which he gave of the capacity of an 

 electrified circular disc. This, of course, has often been quoted before, but 

 it is in no way more remarkable as regards accuracy than many other experi- 

 ments mentioned in this volume. 



Volume two opens with a photograph of Cavendish's house at Clapham. 

 Most of the contents have been derived from manuscripts preserved at Chats- 

 worth. The work was begun several years ago, but the printing has been 

 much delayed. The greater part of it deals with chemical subjects, but, as 

 the editor points out, the general impression that Cavendish was pre-eminently 

 a chemist is erroneous, although his achievements in chemistry are undeniably 

 very great. For in these volumes it becomes clear that he made important 

 contributions to every branch of physical science then in existence. The 

 treatment in the present volume has been arranged as nearly as possible on the 

 lines of Maxwell's treatment of the electrical researches. There is a valuable 

 commentary showing the relation of his work to the general state of knowledge 

 in his time and to the subsequent advances which have taken place. Several 

 of his papers, previously unpublished, indicate that Cavendish anticipated 

 in some cases the results of later experimenters. For example, there is now 

 no longer any doubt that he was the real discoverer of arsenic acid, and that 

 his method is the method in use at the present day. He also was obviously 

 aware of some of the laws which lie behind the phenomena of gaseous diffusion. 

 A point which stands out rather prominently is the clear nature of his views 

 regarding the Conservation of Energy and the degradation of energy into 

 heat. He indeed anticipates much of Helmholtz's famous essay of 1847. Sir 

 Joseph Larmor has made clear the relation of his ideas to those of Newton 

 and Daniel Bernoulli and other writers to whom Helmholtz expressed his 

 obligations. 



Sir Frank Dyson points out the completeness of Cavendish's knowledge of 

 the tidal retardation of the diurnal rotation of the earth and the principle of 

 rotational torque and energy exchange which are relevant. He was indeed 

 aware of the amount of deviation of a ray of light passing near the sun according 

 to the Newtonian corpuscular theory as extended by Mitchell to include 

 gravitation of the corpuscles. 



Dr. Chree gives an account of the magnetic work of Cavendish. Maxwell 

 devoted only a very short summary of this part of his work. Dr. Chree 

 shows that Cavendish anticipated many subsequent observers in, for example, 

 his determination of the best form of dip-needles, by tracing the influence of 

 bending the needle on the observed value of its inclination, and as regards 

 other sources of error. 



Sir Archibald Geikie indicates the extent of Cavendish's contributions to 

 Geology. 



These two volumes are a very notable addition to the rapidly increasing 

 list of scientific memoirs pubUshed by the Cambridge University Press. 



D. Wrinch. 



The Reign of Relativity. By Viscount Haldane. [Pp. xxiii + 427.] 



(London: John Murray, 1921. Price21s.net.) 

 Frankly, this is not a book for those who still hope to see the meaning 

 of Einstein's new work put into popular terms. The theme is that of the 



