April 6, 1900.] 



SCIENCE. 



547 



philosophy, the publication of which in the 

 near future is promised. 



That he was a great genius does not seem to 

 be doubted by his biographer, Mr. E. S. 

 Stevens, who declares that he was not only a 

 great geologist, but also a great philosopher ; 

 that he was " the greatest scientist America has 

 produced," that "he hasleft littleto be accom- 

 plished," and that he has " taken his place be- 

 side Copernicus, Galileo, Newton and Darwin." 



And what is the ' diuturnal motion of the 

 earth ' upou the conception and alleged proof 

 of which so much claim to distinction is made 

 to rest ? No very clear account of it is to be 

 found anywhere in the book, but it is ob- 

 viously intended to mean a slow, progressive 

 movement of the pole of the earth's axis of 

 revolution in a spiral line around the earth's sur- 

 face. Maps are given showing six lines of 

 polar transmission across the Eastern and the 

 Western hemispheres, and the period occupied in 

 passing through one ' curl ' of the sjiiral is as- 

 sumed to be extremely great. This movement 

 of the position of the earth's axis would neces- 

 sarily produce great climatic changes, but in 

 addition to this it is alleged that there would 

 be a shifting of the superficial strata or crust of 

 the earth relative to the interior, and upon this 

 hypothesis is founded an explanation of existing 

 geological phenomena, which, in the judgment 

 of the biographer, ' transforms the patchwork of 

 geology into a complete science.' 



Among numerous illustrations of the au- 

 thor's fitness for discussing problems involving 

 physical and dynamical laws, in which the 

 book abounds, the following may be quoted : 

 " Heat we claim to be material ; it is substance 

 and gravitates towards the center of the earth, 

 constantly keeping an equilibrium between the 

 interior forces and the external atmosphere, 

 with its stratified fields of electricity and mag- 

 netism ; but when that gravitated heat comes 

 in contact with sedimentary deposits, contain- 

 ing a superabundance of compound substances, 

 as vapors, gases and ethers, and liberates these 

 through the action of the chemical processes in 

 that great laboratory of nature, they must 

 find their outlet through established chimneys, 

 as volcanoes, or otherwise make new openings 

 for their ascent to the upper air ; and only in 



events like this would we be willing to at- 

 tribute the phenomena called earthquakes to 

 internal forces." 



Speaking of Galileo the author says, "He 

 discovered that the vibrations of all pendulums, 

 even of different lengths were performed in 

 equal time. * * * He also ascertained the beat- 

 ing of the pulse from this fact and counted it 

 by the vibrations of a pendulum. * * * He dis- 

 covered the thermometer, an instrument by 

 which is measured the expansion or coudensive 

 heat of the atmosphere." 



The author shows considerable familiarity 

 with the literature of science, fx'om which ex- 

 tensive quotations are made, often having little 

 relation to the subject under discussion. 



There is left with the reader a. feeling of re- 

 gret that those who have the means to con- 

 tribute to the advancement of science by the 

 issue of such expensive publications as this 

 should not have sought competent advice from 

 recognized scientific authority before going to 

 the printer and book binder. 



T. C. M. 



Elements of the Differential Calculus. By James 

 McMahon, A.m., Professor of Mathematics 

 in Cornell University, and ViRGiL Snyder, 

 Ph.D., Instructor in Mathematics in Cornell 

 University. New York, Cincinnati, Chicago. 

 The American Book Company. 1898. Pp. 

 xlv + 337. 



We have examined this book with pleasure. 

 It was evidently composed in the light. Peda- 

 gogical and scientific qualities are united in a 

 degree seldom attained in elementary text- 

 books. Sound argument, genuine demonstra- 

 tion, logical concatenation, are seen to be, in 

 general, more consistent, than is commonly 

 supposed, with required simplicity and clear- 

 ness. The claims of the logician, on the one 

 hand, and of the didactician, on the other, are 

 adjusted with notable goodjudgment and skill. 

 Illustrative solutions are numerous and the 

 volume contains a plenty of suitable exercises 

 for the reader, but the book is by no means a 

 mere 'quarry of examples.' Even less, if pos- 

 sible, is it intended to be a guide to the mere 

 practician. On the contrary, the treatment 

 aims first of all at being scientific. The modern 



