October 6. 192 ij 



NATURE 



175 



decimal system, as against the complicated nota- 

 tions now in use in this country, and some have 

 worked out decimal systems which they considered 

 suitable for introduction by Act of Parliament. 

 Dr. Cusack has gone a step further by producing 

 a text-book of arithmetic in which the calcula- 

 tions are all in terms of the decimal notation, and 

 the various quantities dealt with, like length, area, 

 volume, weight, and money, are all decimalised. 



The author does not desire to introduce the 

 nxeiric system. This is merely one form of 

 decimal system, and Dr. Cusack considers that 

 we in this country are so much accustomed to the 

 use of the yard, the hundredweight, the gallon, 

 the pound sterling, etc., that it is necessary to 

 retain these units in any decimal system we em- 

 ploy. The effect of the acceptance of this idea 

 would therefore be merely the abolition of the 

 vulgar fraction in business and other calculations ; 

 the difference between the English and the Con- 

 tinental units would still remain. This is not the 

 place for a discussion of the problem, but it must 

 be pointed out that a considerable fraction of the 

 advantages derivable from such a radical change 

 of our English system of units would be lost if 

 we refused to fall in with the Continental metre, 

 gramme, and litre. As regards money units, the 

 matter is entirely different — international ex- 

 changes have such huge relative time-gradients 

 that it is idle to attempt any international equal- 

 isation of the currency. 



Dr. Cusack's book is excellently written and 

 produced. It is really a piece of propaganda 

 literature, and as such it should have more effect 

 than any number of Parliamentan.- speeches and 

 Chamber of Commerce resolutions in educating 

 public opinion in the direction of accepting a long- 

 overdue reform of our system of units. 



S. Brodetsky. 



Annales de I'Ohservatoire astronomique de Tokyo. 

 Tome 5, 46 fascicule. Studies on Astronomi- 

 cal Time-Keepers and Time-Preserving Systems. 

 By Kiyofusa Sotome. Pp. ii -|- 59. (Tokyo : 

 Imperial University, 192 1.) 



The problem of the determination and distribu- 

 tion of accurate time has been advanced consider- 

 ably in recent years by the use of the moving wire 

 m observing transits, and the introduction of wire- 

 less time-signals. Hence the analysis of the 

 behaviour of high-class time-keepers under various 

 conditions, which is dealt with in this memoir, is 

 likely to be of general utility. Mr. Sotome notes 

 that chronometers are essential in Japanese 

 observatories as a supplement to pendulum clocks, 

 on account of the prevalence of earthquake shocks, 

 which produce abrupt changes on the error and 

 rate of a clock, but have no sensible effect on a 

 chronometer. It is shown that the chronometer 

 rates are sensitive to changes of atmospheric 

 pressure and humidity, so that an air-tight case 

 should be used. Most of the chronometers 

 sho\yed perceptible change of rate according to 

 the inter\al that had elapsed since winding; this 

 NO. 2710, VOL. 108] 



change was diminished by using a falling weight 

 instead of a spring as motive power, a method 

 that is practicable in an observatory, but not at 

 sea. 



The section on pendulum clocks deals not only 

 with those at Tokyo, but also with the records of 

 the standard clocks of several European observa- 

 tories. There is a curious general tendency to 

 acceleration of rate, which may be due to accumu- 

 lation of dust, rust, etc., on the rod and bob. 

 An examination is made of the properties of dif- 

 ferent metals that are used as pendulum rods; it 

 is found that invar is subject to gradual elonga- 

 tion and irreversible thermal expansion ; quartz 

 or tungsten are suggested as suitable. The im- 

 portance of an air-tight chamber, with constant 

 pressure and temperature, is emphasised. 



Finally, the memoir deals with the determina- 

 tion of true time, which involves the distribution 

 of error between the transit observation and the 

 timepiece. It is suggested that abnormalities in 

 the former may sometimes be due to lateral refrac- 

 tion, arising from unsymmetrical temperature dis- 

 tribution. The ratio of probable errors of the 

 observed transit and the assumed clock rate 

 having been found by experience at each obser\'a- 

 tory, formulae are given for obtaining a weighted 

 mean clock error. 



A. C. D. Crommelix. 



String Figures. By W. W. Rouse Ball. Second 

 edition. Pp. 69. (Cambridge : W. Heffer and 

 Sons, Ltd., 1921.) 25. 6d. net. 



This book is a second and enlarged edition, of 

 which we have already noticed the first issue 

 (Nature, vol. 106, p. 640). The subject is com- 

 paratively new, though one variety, the cat's 

 cradle, has a literary pedigree from the eighteenth 

 century, and the boys at Christ's Hospital used 

 to play it in the time of Charles Lamb, as related 

 by that charming writer in his essay on the famous 

 foundation ; but the discovery of the more interest- 

 ing forms dates from the Cambridge expedition to 

 Torres Straits in 1898 under the leadership of 

 Drs. Haddon and Rivers. Since then many in- 

 teresting figures have been recorded, notably in 

 America, by Mrs. Jayne. 



The invention is certainly due to the lower 

 culture, and the distribution of the figures is very 

 interesting. That known as " Lightning " comes 

 from the Navaho Indians of Arizona ; the now 

 almost extinct Apaches passed on the "Tent 

 Flap " to the Mexican Indians; "Man Climbing a 

 Tree " comes from the Queensland blacks ; the 

 " Batoka Gorge " was accidentally discovered by 

 someone who showed some other figures to the 

 native police escort at the Victoria Falls. In 

 fact, as Mr. Ball tells us, no self-respecting an- 

 thropologist ought to go about without a piece of 

 string in his pocket. As anyone can now learn 

 a fascinating game under his careful guidance, 

 it may be hoped that field anthropologists will 

 soon tell us more about its various methods and 

 its origin. 



