264 



NATURE 



[June 6, 19 18 



Transmission Gears, Mechanical^ Electric, and 

 Hydraulic, for Land and Marine Purposes. By 

 E. Butler. Pp. xii+164. (London: Charles 

 Griffin and Co., Ltd., 1917.) Price 8s. 6d. net. 

 This book is intended for engineers engaged in 

 the application of internal-combustion engines for 

 automobile, marine, and other purposes, and pro- 

 vides a fairly exhaustive treatment of friction- 

 clutches, change-speed gears, and reversing 

 methods. The book contains a large number of 

 illustrations taken from vi'orking drawings; these 

 drawings, together with the accompanying de- 

 scriptions, constitute the most valuable part of 

 the work, and should be very useful from the 

 designer's point of view. The author is by no 

 means so happy in the sections introducing calcu- 

 lations, and in some parts has produced so much 

 confusion as to. render these portions almost un- 

 readable. Thus the terms "torque " and "driving 

 effort" have entirely different meanings, but the 

 author uses them indiscriminately in his calcula- 

 tions on friction-clutches. The result is that there 

 are many errors in this section of the book, which 

 should be revised thoroughly in the second edition. 

 Further, calculations which "run on" in the text 

 are difficult to follow ; these are much more likely 

 to be read and understood if displayed properly. 

 There is also need for the introduction of clear 

 methods of calculating epicyclic gears ; those given 

 are not likely to be of much assistance to the 

 designer. As stated above, the value of the book 

 consists in its collection of working drawings, and 

 its value could be greatly enhahced by thorough 



revision. 



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 communications.'] 



Construction for an Approximate Quadrature of the 

 Circle. 



Dr. Rouse Ball's interesting account, in Nature of 

 May 23, of M. de Pulligny's constructions reminds 

 me of another simple one which I do not think known. 

 If OA, OB are perpendicular radii of a circle of 

 radius i, and if BCD is a line cutting OA in C and 

 the circle in D and representing the side of the square 

 in question, then OC = ^(4/ff- i) = o-5227232i, which, 

 put into the form of a continued fraction, has for 

 convergents 1 l\, i§, ff, f?|Q, etc. The convergent |2» 

 or 052272727, differs (in excess) from the real 

 magnitude only by i in 128750; hence if we take C 

 such that OC=ffOA, which can be done easily and 

 with great accuracy, the line BCD represents the 

 required side with all the accuracy which anv graphic 

 construction can be expected to give. Theoretically, 

 this method is 121 times more accurate than M. de 

 Pulligny's construction with the Archimedes ratio, but 

 thirty-seven times less accurate than that with the 

 Metius ratio. In practice, however, this relative in- 

 accuracy is absolutely unnoticeable, and the method 

 here described is the easier to carrv out. 



Robert E. Baynes. 



Christ Church, Oxford. 



NO. 2536, VOL. IO1I 



The " Wolf •note " in Pizzicato Playing. 



The accompanying photograph, showing the simul- 

 taneous vibration curves of the G string and bridge 

 of a 'cello played pizzicato at the "wolf-note" pitchy 

 presents some noteworthy features which may be of 

 interest to readers of Nature. One of the striking, 

 features is the extremely rapid dissipation of energy. 

 The other feature is the effect of the motion of the 

 bridge on the vibration of the string. The photograph 

 may, in fact, be briefly described as showing a strongly 



damped coupled vibration of the string and bridge, in 

 many respects differing from the cj^clical vibrations ex- 

 cited by Solving at the " wolf-note " pitch described by 

 me in previous communications to Nature. At pitches, 

 slightly different from that of the "wolf-note," the 

 dissipation of energy is far less rapid, and the motion 

 of the string approximates to that of an ordinary 

 damped harmonic vibration. C. V. Raman. 



Calcutta, April 12. 



The "Hay-box" Principle in Cooking. 



It happened last week that about i lb. of fresh lamb 

 was put .into an oven at night in order that it might 

 be cooked by morning on the "hay-box" principle. 

 It was in a casserole, with a little water." Similar 

 treatment in the same oven on previous occasions had 

 been very successful. At about 5 a.m. the casserole 

 was examined, and the broth' was found to be very 

 well tasted, and the whole smelt fresh and good, but 

 the meat when tested with a fork was not tender, and' 

 the fat (of which there was a good deal) was entirely 

 unmelted. The casserole was returned to the oven 

 (then quite cool) and taken' out again after breakfast.. 

 The contents were then found to be smelling most 

 offensively, as if extremely " high." The fat was^^ 

 melted. The meat and broth were judged quite unfit 

 for human food. 



I wonder if any of your readers would explain this; 

 curious development. An Inquirer. 



May 30. 



British Oligochaet Worms. 



I AM now engaged on the MS. of my monograph- 

 of British Oligochaets for the Ray Society. The first; 

 volume will be devoted to the Enchytrgeids or white- 

 worms. Though the country has been well worked, 

 no doubt there still remain indigenous species whicb 

 have not yet been recorded ; and I shall be glad tc 

 aid other workers in making them known. 



HiLDERic Friend. 



Cathay, Solihull, Birmingham. 



