394 



NA TURE 



[February 4, 1509 



GRAPHICAL HYDRAULICS. 

 Water Pipe and Sen'er Discharge Diagrams. By T. C. 



Ekin. Pp. 21. (London : Archibald Constable and 



Co., Ltd., 1908.) Price 12s. 6d. net. 

 /~\F all empirical formula devised for the solution 

 of practical problems in natural science, hydraulic 

 formulffi are perhaps the most involved and complex, 

 and of all hydraulic formulae it is doubtful whether 

 there be a more formidable expression than the 

 coefficient in Ganguillet and Kutter's formula for the 

 tlow of water in pipes and channels. 



The general expression, and that which is now com- 

 monly recognised as furnishing the most trustworthy 

 basis for the estimation of current velocity in such 

 cases, is the equation devised by Chezv towards the 

 close of the eighteenth century, viz. V = Cv/RS, in- 

 volving- the hydraulic mean depth (R) and the sine of 

 the slope (S) in conjunction with a coefficient C. 



.As determined by the classical researches of Gan- 

 guillet and Kutter (the formula is more generally asso- 

 ciated with the name of the latter only of the two 

 eminent Swiss experimentalists), the coetificient takes 

 the form : — 



/ 



HI which a, !, and in are respectively in English units, 

 41-660475, 1-811325, and 0-0028075, and n is a variable 

 depending upon the degree of roughness of the surface. 



The labour involved in working out casually, and as 

 necessity arises, a particular value from so cumbrous 

 an expression is sufficiently obvious, and it is not 

 surprising that a number of attempts have been made 

 to supply some ready solution applicable to different 

 d;ita by the construction of curves and graphical 

 diagrams. 



The author points out that hitherto such curves have 

 not dealt with gradients exceeding 5 per :ooo, and 

 that steeper gradients are often required. He has, 

 therefore, worked out a series of curves giving the 

 discharges of pipes ranging from 3 to 48 inches in 

 diameter, and the velocities, when running full, on 

 gradients from 5-28 feet per niile, i in 1000 or i per 

 1000, up to 79-2 feet per mile, i in 66-6 or 15 per 

 1000, and embodied the results in four large diagrams 

 in which each discharge curve is the result of twenty- 

 two separate calculations, and each velocity curve has 

 been calculated for each point in which it cuts the 

 discharge curve. 



These diagrams are not strictly derived from 

 Kutter's original formula, but from Flynn's modified 

 statement of it, with n and S ( = o-ooi) taken as con- 

 stant throughout the series of curves, and VR varying 

 with each diameter of pipe. The coefficient of rough- 

 ness of surface (ii) has been fixed at 0-013, as most 

 applicable to practical work under ordinary conditions. 

 There are a number of cases, however, in which pipes 

 calculated with this value give results either too large 

 or too small, and with the view of making the dia- 

 grams apply to several coefficients of roughness, the 

 author has calculated a series of constants, embodied 

 in a separate table. Tliere are six tables in al), forrn- 

 NO. 2049, VOL. 70I 



ing an appendix, yielding detailed information respect- 

 ing pipe flow and hydraulic data generally. 



The compilation should prove of great utility to 

 those engaged upon problems of water supply, sewage 

 disposal, and practical problems of a kindred nature. 



BRITISH OAK GALLS. 

 British Oa): Galls. By E. T. Connold. Pp. xvili + 

 169; 68 plates. (London: .Adlard and Son, 1908.) 

 Price los. 6d. net. 



MR. E. T. COXNOLD has already given us a 

 very valuable work on " British Vegetable 

 Galls," but in that work, as the author states in 

 the preface, the galls of the oak are not included, as 

 he intended to publish a separate book dealing with 

 them. This book has now appeared, and in every 

 way it conies up to the standard of the larger work. 

 .\ great feature of the book is the many life-like and 

 excellently reproduced photographs of actual speci- 

 mens of galls. 



The oak is the abode of some five hundred different 

 species of insects and other animals which subsist 

 mainly on the leaves. Some are parasitic on the 

 larvffi of the gall makers, and others are inquilines. 

 which subsist on the tissues of the galls. 



In his introduction the author touches upon some 

 historical matters, and in chapter i. several very in- 

 teresting and at present not fully understood pheno- 

 mena in connection with the formation and colours of 

 galls are discussed. Chapter ii., which deals with 

 the characteristics of oak-gall growth, such as posi- 

 tion, duration of growth, variations in shape, size and 

 colour, &c.. is also a very interesting chapter to the 

 student of oak galls. 



Chapters iii. and iv. deal respectively with the 

 numerical aspect of oak galls and the Cynipidae 

 affecting the oak. The latter chapter is intended to 

 present in a concise form such information as may be 

 necessary for the collector or student who may not 

 have ready access to other books which deal with 

 these interesting and remarkable insects. 



Chapter v. gives a short description of the genus 

 Ouercus, and especially of the British oak. In 

 ciiapter vi. many useful hints on the collecting and 

 mounting of oak galls are given. The rest of the 

 book deals individually with the various species 

 which cause oak galls. A synoptical table is given, 

 also a table of the months in which the galls illus- 

 trated in the book may be found. A list of mid- 

 European oak galls, with brief characteristics and 

 position the gall occupies on the tree, is added, and 

 will prove a great help to many. A useful index is 

 also included. 



This volume, the author tells us. is the outcome of 

 fifteen years' study and practical research in the 

 field. He is glad to say that he has been able to 

 describe several galls not mentioned in any other 

 English publication. Still, in spite of this great 

 amount of time and study, the author does not claim 

 completeness for his work. In the preface he says :^ 



" There is much more to be ascertained concerning 

 the growth of oak galls, and one purpose of the 



