NA TURE 



47, 



THURSDAY, SEPTEMBER 17, igoS. 



SEWAGE WORKS. 



The Design, Construction, and Maintenance of Sewage 

 Disposal Works. By Hugh P. Raikes. Pp. xv+ 

 414. (London: Archibald Constable and Co., Ltd., 

 1908.) Price 16s. net. 



THOSE entrusted with the design and construction 

 of sewage works should have at their disposal 

 the latest results of contemporary science to guide 

 them, and the author's contention that no other book 

 has recently been published from which equally full 

 and trustworthy information can be obtained by the 

 engineer is substantially correct, with the reservation 

 that the information alluded to has reference to recent 

 developments. Judged from this standpoint, the 

 volume is likely to appeal to the engineer, since it 

 summarises a considerable amount of recently acquired 

 knowledge relating to sewage disposal, and contains 

 the advice and experience of one who has had to face 

 the practical problems involved. 



From the circumstance that the work contains much 

 elementary matter, more especially in the opening 

 parts, it appears that it is not designed exclusively for 

 advanced students ; and that being so, this matter 

 should be extended so as to meet the needs of those 

 who approach the subject with comparatively little 

 knowledge ; for some of the bacteriological and 

 chemical references in this volume are insufficient for 

 the student's comprehension as they stand at present, 

 and in some cases they demand revision in a subse- 

 quent edition. 



To give instances, on p. 162 it is stated that " the 

 best results have been obtained with a solution of 

 bleaching powder containing hypochlorite of calcium 

 having 36'35 available chlorine." On p. 143 the value 

 of copperas as a chemical precipitant is discussed in 

 a way which infers that its main virtue depends upon 

 its acidity and the fact that its use in conjunction 

 with lime prevents an excessively alkaline effluent. 

 On p. 31 the author states that " the difference in the 

 composition of sewage in different places may be as 

 great as that between milk and writing ink." While 

 conceding that great differences exist, the comparison 

 is, to say the least, an unhappy one. There is no 

 chemical or physical justification for it. 



On p. 35 the author remarks, with reference to 

 sewage effluents, that " the presence of a few disease 

 germs cannot be considered of vital importance so far 

 as water supplies are concerned when the water is 

 again filtered before use." On p. 52 he states that 



" the danger of disease cannot be indicated by the 

 mere numbers of any particular disease-producing 

 micro-organisms that may happen to exist, in samples " 

 — of polluted water or shell-fish — " so that for the 

 present, at any rate, topographical observations must 

 be_ regarded as the only reliable means of detecting 

 objectionable contamination. " 



The following statement on p. 71 is not very clear :— - 

 " It would therefore seem to be a very much simpler 

 matter to sterilise the shell-fish or water supplies than 

 NO. 2029, VOL. 78] 



to deal with sewage effluents in this way, as no such 

 system could be relied upon to remove all danger of 

 contamination, and the consumers would still have to 

 rely for protection on those who supply them with 

 water or shell-fish as the persons directly responsible 

 for their freedom from contamination." 



The author very justly directs attention to the cir- 

 cumstance that local authorities all too frequently 

 appoint as managers of sewage works individuals 

 who have neither an adequate understanding nor ap- 

 preciation of the duties appertaining to such a post, 

 nor the qualifications which are necessary to enable 

 them to fulfil those duties satisfactorily. He then 

 proceeds to lay down some of the qualifications which 

 a good manager should possess ; and one is astonished 

 to find the following paragraph on p. 367 : — 



" The increasing attention now being devoted to 

 the study of bacteriology in connection with sewage 

 disposal also renders it highly desirable that a manager 

 should understand the methods of cultivating, count- 

 ing, and distinguishing the different kinds of bac- 

 teria to be found in sewage, so that he may be able to 

 observe the conditions that are favourable or unfavour- 

 able to their growth, and thus ascertain the best means 

 of developing the growth of those which are useful 

 for decomposing the sewage while at the same time 

 destroying the pathogenic or disease-breeding bacteria, 

 which may sometimes constitute an even greater source 

 of danger in the final effluent than chemical im- 

 purity." 



Placing the broadest construction upon the above 

 sentence, how many expert bacteriologists in this 

 country possess the knowledge held to be highly desir- 

 able in a manager of sewage works ? 



Chapters vii., viii., and ix., dealing with contact 

 beds and percolating filters, may be singled out as the 

 best in a volume which, from the engineering stand- 

 point, justifies its appearance. It cannot fail to prove 

 useful to those engineers who do not possess a first- 

 hand knowledge and experience of sewage disposal, 

 for the practical engineering facts are sound and up- 

 to-date, and the requirements of the Local Government 

 Board, the reports of the Royal Commissions, &c., 

 are usefully summarised within the volume. 



MATHEMATICAL INSTR UCTION. 



A Study of Mathematical Education, including the 

 Teaching of Arithmetic. By B. Branford. Pp. 

 xii + 392. (Oxford: Clarendon Press, 1908.) Price 

 4s. 6d. 



BY far the most valuable part of this book consists 

 of the examples which it gives of the curiously 

 limited powers of generalisation and abstraction pos- 

 sessed by young pupils. For example (p. 44), a class, 

 after experimentally adding angles together, agreed 

 that four angles could be added, but not five. A still 

 more remarkable case is described on pp. 304-9. A 

 little girl was given three congruent paper triangles 

 .\ B, C ; after fitting A to B and A to C, she not only 

 failed to draw the conclusion that B could be fitted 

 to C, but refused to admit the force of arguments to 

 that effect. This result was confirmed by experiment 



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