912 



SCIENCE. 



[N. S. Vol. VIII. No. 208, 



the knowledge that enables us to anticipate the 

 rise and fall of the ocean ? How are the tidal 

 tables of the daily papers and of ' The Farmers' 

 Almanac ' constructed ? 



■ It was the primary object of the lectures of 

 Professor Darwin to answer such questions ; to 

 explain in a popular way, without the aid of 

 mathematical and physical technicalities, how, 

 from observations of the tides and from the 

 modern theory thereof, predictions of the rise 

 and fall of the ocean at any port may be issued 

 years in advance. In addition to these more 

 obvious tidal phenomena he has also discussed 

 the more recondite phenomena of bodily tides 

 in the earth and other members of the solar 

 system. Thus, from questions of commercial 

 or otherwise purely practical significance, the 

 reader is led up to questions in cosmology of the 

 highest scientific importance, especially in their 

 bearings on the remote history, past and future, 

 of our planet. 



The task which Professor Darwin set for him- 

 self was a difficult one. Few, if any, questions 

 in the mathematico-physical sciences are more 

 profoundly complicated than those presented by 

 tidal phenomena. Their elucidation has taxed 

 the ingenuity of the most laborious investigators 

 from the time of Newton to the present day. 

 lu the highly condensed language of mechanics 

 it may be said that these phenomena, in any 

 case, are simply the outcome of the energy, the 

 angular momentum and the friction involved. 

 But to turn conclusions expressed in such lan- 

 guage into common parlance would seem to be 

 almost as great a work as that of reaching the 

 conclusions themselves. No one less well 

 equipped than Professor Darwin would have 

 dared to undertake this task. Thoroughly 

 familiar with the details of tidal action, and 

 himself a principal contributor to recent ad- 

 vances in tidal theories, he has produced a 

 charmingly interesting and instructive book, 

 which may be read with profit by those who 

 know much as well as by those who know little 

 of the tides. 



The book is divided into twenty chapters 

 under the following titles : Tides and Methods 

 of Observation, Seiches in Lakes, Tides in 

 Rivers— Tide Mills, Historical Sketch, Tide- 

 generating Force, Deflection of the Vertical, 



The Elastic Distortion of the Earth's Surface by 

 varying Loads, Equilibrium Theory of Tides, 

 Dynamical Theory of the Tide Wave, Tides in 

 Lakes — Cotidal Chart, Harmonic Analysis of 

 the Tide, Eeduction of Tidal Observations, Tide 

 Tables, The Degree of Accuracy of Tidal Pre- 

 diction, Chandler's Nutation — The Rigidity of 

 the Earth, Tidal Friction, Tidal Friction (con- 

 tinued). The Figures of Equilibrium of a Ro- 

 tating Mass of Liquid, The Evolution of Celes- 

 tial Systems, Saturn's Rings. Each chapter is 

 followed by a list of authorities on the subject 

 of the chapter, and a good index completes the 

 volume. -^ s_ ^^ 



The Elements of Physics. By Alfred Payson 



Gage. Boston, Ginn & Co. 1898. 12mo. 



Pp. x+SSl. 



The author of this book put forth his first 

 edition sixteen years ago and has long been 

 favorably known as a reliable authority in the 

 schoolroom. The motto then adopted, 'Read 

 Nature in the Language of Experiment,' is 

 very properly retained in the present volume, 

 which is not a revision, but a new book differing 

 quite radically from the first in its method of 

 presentation. The change, moreover, is a great 

 improvement. We all agree that the experi- 

 mental method is the proper method of investi- 

 gating what is collectively called Nature, but 

 there has been much diiference of opinion about 

 the advisability of regarding elementary pupils 

 in the high school as fit to acquire their funda- 

 mental conceptions of physics by independent 

 discovery. In the preface to the present vol- 

 ume Dr. Gage repeats the expression of his be- 

 lief in the importance of the laboratorj"^ method 

 in the high school, but adds that he has ' ob- 

 served the development of a tendency which 

 threatens seriously to impair its usefulness.' 

 He is now ' convinced that both mental disci- 

 pline and the acquisition of knowledge will be 

 promoted if theory and experiment be some- 

 what sharply divided.' 



There are a good many of us who have long 

 held this last view in opposition to that which 

 was carried out in Dr. Gage's first book. The 

 demand for laboratory methods in the school 

 room is much more than sixteen years old. A 

 protest against the abuse of them was distinctly 



