May 13. 1909] 



NA TURE 



307 



retains its place by a convention which remains valid 

 owing to the force of longf-continued custom. If the 

 fluctuations in prices as measured by it became too 

 great, it would have to be discarded as a standard 

 of value. T. K. R. 



Arlifuial ]yaterways and Commercial Development 

 {tvith a History of the Erie Canal). By, Dr. A. 

 Barton Hepburn. Pp. i.\+ii5. (New York: The 

 Macmillnn Co. ; London : Macmillan and Co., Ltd., 

 ii)Oq.) Price 45. net. 

 AiiFR a long period of effacement, artificial water- 

 wavs are beginning to regain some amount of public 

 interest' and concern. The advent and rapid develop- 

 ment I if railways during the last century was re- 

 sponsible for their relegation into a background of 

 indiU'erence and neglect, and so long as men's minds 

 were dominated by schemes of rapid locomotion at 

 any cost, it was difficult, and, in fact, impossible, for 

 canals to maintain any footing in competition with 

 a system of transit infinitely more expeditious and 

 direct. But a change is taking place in public feeling. 

 It is being recognised that canals have been at an 

 undue disadvantage, and that, as a means of loco- 

 motion, they possess features which merit encourage- 

 ment and development. Inland water carriage for 

 goods, though slow, is safe and cheap, and canals 

 possess a striking advantage over lailways in that, in 

 place of isolated depots at long intervals, they possess 

 a continuous frontage workable throughout their 

 entire length. On these and other grounds, public 

 interest in canals has been aroused, and a Royal Com- 

 mission in this country has lately had under considera- 

 tion the means best adapted for their revival and 

 amelioration. 



Dr. Hepburn's book is a timely contribution to the 

 evidence on the subject. Written from an American 

 standpoint, it constitutes an appeal to the citizens of 

 the United States in regard to the development of 

 their artificial waterways. It recites in brief com- 

 pass the principal historical facts connected with 

 canals throughout the world, and then proceeds to 

 consider in more extended detail the canal system of 

 New York, describing its inception, development, and 

 present condition. Thence the author passes, by a 

 transition natural to a patriotic American, to an 

 account of the Panama Canal, with its vicissitudes 

 and possibilities. The volume closes with fifteen 

 statistical appendices. 



I-Jvilrographical Sur'eeyiiig. A Description of Means 

 and Methods employed in constructing Marine 

 Charts. Bv the late Rear-Admiral Sir William 

 J. L. \\'harton, K.C.B. A new edition, revised and 

 enlarged by Rear-Admiral Mostyn Field, F.R.S. 

 Pp- viii + 475. (London: John Murray, 1909.) Price 

 21S. net. 

 TiiF. late Admiral Wharton's " Hydrographical Sur- 

 veying," which has been for so many years a standard 

 work and one of the best books for surveyors that 

 has ever been published, has now been brought up 

 to (late by his successor, Rear-Admiral Mostyn Field, 

 the present hydrographer to the Admiralty. Admiral 

 Field has endeavoured to alter the text of the former 

 work as little as possible, but at the same time to 

 enlarge it considerably by the addition of new features, 

 including expedients connected with work in the field 

 wiiich have been found useful in practice, in order 

 especially to assist the young surveyor bv directing 

 his attention to useful methods of procedure which 

 otherwise he would only pick up as his experience 

 ripened. In addition to these features, all the latest 

 improvements are fully described, such as the use 

 of photography for the reproduction of charts, auto- 



NO. 2063, VOL. 80] 



niatic tide gauges, improved instruments for observ- 

 ing currents and taking deep-sea soundings, and, 

 finally, the usefulness of the Barr and Stroud range- 

 finder for surveying purposes. 



The volume as it now appears, brought thoroughly 

 up to date and accompanied by excellent diagrams', 

 cannot fail to be of the utmost value to all surveyors. 



H. C. L. 



CEuvres completes de Christian Huyghens puhliies 

 par la Society hollandaise des Sciences. Vol. xi., 

 Tr^-jvaux mathematiques, 1645-1651. Pp. iv+369. 

 (La Haye : Martinus Nijhoff, 1908.) 

 This volume is divided into several parts. The first 

 part deals with Huyghens's early writings (1645-6), 

 and is preceded by an account of a manuscript by 

 van Schooten which formed the basis of Huvghens's 

 first mathematical studies. The writings in ques- 

 tion deal, inter alia, with elementary geometrical 

 considerations relating to the parabola and funicular 

 polygons. The next portion consists of Huyghens's 

 three books entitled " De iis quse liquido supernatant " 

 (1650), forming a collection of applications of the 

 principle of Archimedes to floating bodies of simple 

 shapes. A number of geometrical problems dated 

 1650 follow, and the volume concludes with the 

 " Thporemata de quadratura hyperboles, ellipsis, et 

 circuli ex dato portionum gravitatis centro " (1651). 

 The volume is well got up, and forms an interesting 

 contribution to the history of mathematics. 



The General Characters of the Proteins. By Dr. 

 S. B. Schryver. Pp. x4-86. (London : Longmans, 

 Green and Co., 1909.) Price 2S. 6d. net. 

 This is another of the series of monographs on 

 biochemistry which are being issued by Messrs. Long- 

 mans under the editorship of Drs. Hopkins and 

 .\ders Plimmer. The previous monographs have been 

 already noticed in these columns, and two of these 

 dealt with the proteins from the more strictly chemical 

 point of view. Dr. Schryver now adds another 

 chapter to, and by no means exhausts, this large 

 subject. The first section deals with the physical 

 properties of the proteins (solubilities, crystallisation, 

 heat coagulation, rotatory power, electrical conduc- 

 tivity, and so forth) ; the second with their general 

 chemical characters (tests, distribution of nitrogen, 

 compounds with acids, bases, halogens, &c.) ; and the 

 third with the precipitin reaction, which is com- 

 monly known as the biological test. 



The whole is treated in a technical but clear 

 manner; references are given to the authorities quoted, 

 and the booklet will prove a useful addition to the 

 library of the physiologist, and should be found in 

 every laboratory devoted to biochemical research. 



W. D. H. 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous coinmunications.] 



The Gravitative Pull upon the Moon. 



The error made by Mr. McLennan in N.wure of May 6, 

 p. 276, is a curious one, which may perhaps be made 

 more often than we are aware of, and therefore is worth 

 correcting. 



It is true that gravitational pull and centrifugal force 

 both decrease as square of distance increases, each with 

 its own cause of decrease, so as to remain equal and 

 opposite ; but then the two causes of decrease are not to 

 be piled on to one of those forces ! That is the error. 



