November 28, 1901] 



NA TURE 



75 



the same year he says that he often wonders how Newton 

 could take the trouble to make so many researches and 

 difficult calculations which have no foundation but this 

 principle of universal attraction, which seems to him an 

 absurd one. 



With Leibnitz, Huygens was in fairly constant corre- 

 spondence during the year 1690, chiet^y on the subject 

 of the differential and integral calculus, to which Leib- 

 nitz invited his attention ; these letters have already 

 been published more than once, but are here illustrated 

 by several extracts from the notebooks of Huygens. 

 After the publication of the "Traite de la Lumiere" in 

 1690 (written in Paris twelve years earlier), Leibnitz 

 wrote to express his surprise at, and satisfaction with, 

 the undulatory theory, adding that when he saw how 

 well it accounted for double refraction he passed from 

 esteem to admiration. Papin also wrote to express his 

 general approval, but otherwise there are very few allu- 

 sions in the correspondence to the wonderful theory of 

 Huygens, which had to lie dormant for more than a 

 century before it even began to be seriously examined 

 and to gain adherents. It is very curious that Newton 

 should reject the undulatory theory of light while 

 Huygens refused to accept the theory of universal gravi- 

 tation, on both of which theories our modern natural 

 philosophy is founded. But while the objections of 

 Huygens did not retard the progress of the theory of 

 gravitation, Newton's rival theory of light is certainly 

 responsible for the long neglect of the true theory set 

 forth by his Dutch contemporary. 



Among the subjects which throughout Huygens' life 

 continued to occupy his mind the improvement of clocks 

 held one of the foremost places, and he never ceased to 

 hope that in this way the important problem of finding 

 the longitude at sea might be solved. Already, in 1662, 

 he had his clocks tried at sea on a voyage from The 

 Hague to London, but the attempt was a complete 

 failure. Although he had in the meantime made the 

 important invention of spiral-spring balances, he felt that 

 even with this essential improvement no watch was to 

 be trusted on a long voyage owing to the great influence 

 of changes of temperature on the rate, and he therefore 

 determined to try his pendulum clocks again at sea. In 

 1685 he cruised in the Zuyder Zee with two clocks sus- 

 pended from the ceiling of the cabin in gimbals, and 

 though the sea was very rough one of the clocks kept 

 going the whole time. Encouraged by this success and 

 being assured that the motion of a large ship would be 

 far less violent than that which one of the clocks had 

 been able to withstand, he had the experiment repeated 

 in the following year in a ship belonging to the Dutch 

 East India Company on a voyage to the Cape, giving 

 the captain very detailed instructions as to the manage- 

 ment and rating of the clocks. On the return of the 

 Alcmaer in 1687 he learned that the clocks had kept 

 going, though not as regularly as he had hoped. Huy- 

 gens sent a lengthy report to the Company, with a large 

 chart (reproduced in this volume) showing the track of 

 the ship, first as estimated by the pilots, then as calcu- 

 lated by means of the clocks (passing right across Ireland 

 and far to the east of the first one), and finally the same 

 "allowing for the centrifugal force of the earth." This 

 last track agrees fairly well with that laid down by the 

 NO. 1674, VOL. 65] 



pilots. The matter was not lost sight of in the following 

 years, notwithstanding the many other occupations of 

 Huygens, and at the end of the volume we find again 

 a number of letters exchanged between him and Graaf, 

 who had brought the Alcmaer home from the Cape and 

 who was then about to try the experiment again in 

 another ship. But a great many years were to pass 

 before Harrison solved the problem in quite a different 

 manner. 



It is impossible to read this splendid edition of Huy- 

 gens' correspondence without being struck with the great 

 care bestowed by the editors on their work. Through- 

 out the volumes every allusion to persons, to contem- 

 porary events or to scientific matters is explained and 

 commented on in footnotes, often of considerable length, 

 which form a most valuable adjunct to the work. At the 

 head of each letter it is stated where the original is to be 

 found, whether it has been previously printed, and what 

 letter it is in reply to or which one contains the reply 

 to it. Future historians of the science of the seventeenth 

 century will, indeed, have cause to thank the Haarlem 

 Society of Science and especially the editors to whom 

 this national undertaking has been confided. 



In addition to the chart already mentioned, the volume 

 contains a plate with views and plans of Hofwijck, where 

 Huygens spent the last seven years of his life, and as 

 frontispiece a fine portrait of the elder Constantyn 

 Huygens from a drawing by his great son. 



J. L. E. D. 



ELEMENTARY BOTANY. 



A Laboratory Course in Plant Physiology. By William 

 F. Ganong, Ph.D. Pp. vi-M47. (New York : Holt 

 and Co., 1901.) 



Methods in Plant Histology. By Charles J. Chamber- 

 lain, Ph.D. Pp. viii -F 159. (Chicago: University 

 Press, 1 90 1.) 



First Studies of Plant Life. By Geo. Francis Atkinson, 

 Ph.B. Pp. xii -t- 266. (Boston, U.S.A. : Ginn and Co., 

 1901.) Price 2y. bd. 



DR. G.ANONG seems to us to express sound views 

 on the teaching of science in general and of plant 

 physiology in particular, and the remarks on pp. 9 and 

 10 of his introduction might well be taken to heart by 

 teachers ; the same observation applies to his section on 

 " Teaching and Learning," and careful consideration of 

 the rest of this interesting manual convinces us that the 

 author has much of the spirit of the true teacher in him. 

 In other words, he has a share of that genius which calls 

 forth from his students the desire to do something more 

 than merely gather the opinions and statements of others 

 as to the meaning of all those movements, e.xchanges of 

 matter, increases in size and alterations in volume, &c., 

 which constitute life. 



It seems to us that a student who conscientiously 

 works through the subject of this book, in the manner 

 inculcated by the text and imbued with the spirit of 

 inquiry manifested by the author, must learn much that 

 is worth learning, both on account of its value as know- 

 ledge of the ways of living plants and on account of its 

 significance in philosophy. 



The experiments are as a rule simple, to the point, and 



