364 



NA TURE 



[February 16, 1899 



take in order that the requirements of the various Rivers 

 Commissioners may be complied with. 



The second book is drawn up on essentially different 

 lines ; it is written by a practical engineer, and is largely 

 the outcome of his own experience, though he does not 

 pretend to confine his statements to those based on his 

 own personal observation. On going over the work one 

 cannot but be struck by the fact that, although it is 

 intensely practical, and should prove of very great assist- 

 ance to young engineers, clerks of works, and in fact to 

 all who have to do with sewer construction, the inform- 

 ation is so arranged that it may be utilised in the class- 

 room for the instruction of engineering pupils ; for the way 

 in which the author treats the three parts of his subject — 

 designing, construction, and maintenance — must com- 

 mend itself not only to the practical engineer, but to the 

 teacher in the technical institute and the engineering 

 college. 



As regards the requirements of a system of sanitary 

 sewerage, Mr. Folwell lays down the two propositions : 

 (i) that sewage, and all the sewage, be removed with- 

 out any delay to a point where it may be properly 

 disposed of; (2) that it be so disposed of as to lose, 

 permanently, its power for evil. He describes in order 

 the various methods that from time to time have been 

 adopted to attain these ends. Dry sewage methods and 

 systems, pneumatic systems, water carriage systems, 

 combined and separate systems — first speaking generally, 

 and then giving in some detail the principles involved in, 

 and the data required for, successful sewage disposal, 

 as regards amount of sewage, the flow in sewers, flushing 

 and ventilation, the design, detailed plans, specifications, 

 contract estimate of cost, &c. In a second part, devoted 

 to construction, he goes into the question of preparation, 

 laying out the work, oversight and measurement of work, 

 and practical sewer construction. In the third part he 

 speaks specially of maintenance, of house connection and 

 drainage, and of the maintenance of the sewer itself, 

 dealing specially with flushing and cleaning. 



Many parts of this work w ill be useful to engineers and 

 surveyors in this country, as the question of sewage dis- 

 posal is, in many of its aspects, the same in America as 

 in Europe, and the following " aphorisms " appeal to all 

 alike : " Many diseases may be contracted by taking 

 into the stomach certain germs which are found to be 

 excreted by those already sick of such a disease, and 

 these germs will exist for days in sewage having any 

 amount of dilution"; "ordinarily sewage does not 

 putresce until from twenty-four to sixty hours after its 

 discharge"; " the only true destruction of the dangerous 

 characteristics of sewage is that effected by oxidation and 

 by removal of the disease-germs"; "oxidation does not 

 destroy but merely transforms the putrescible organic 

 matter into harmless mineral compounds"; and so on. 



It is very strongly insisted that corporations are per- 

 haps more inherently selfish than are single individuals, 

 and that consequently corporations have little hesitation 

 in offending their neighbours, or interfering with their 

 hygienic conditions, if they can only manage to do this 

 to their own advantage from a health point of view ; and 

 we are glad to see that he insists that engineers should 

 carefully guard themselves against fostering this weak- 

 ness of those who are their clients. As an example of 

 NO. 1529, VOL. 59] 



the different conditions that hold in America and in this 

 country, one has only to turn to the consumption of water 

 in certain of the large cities to know that in most cases 

 the .American sewage is far more dilute than the sewage 

 running in the drains of our own large cities. From a table 

 given, including twenty-five American cities, it is seen that 

 there are only three that have a water consumption of under 

 fifty-five gallons per head, whilst eleven cities consume 

 over one hundred gallons per head — from one hundred 

 and twelve to one hundred and ninety-nine gallons ; then, 

 too, the consumption is rising steadily from 10 to 100 per 

 cent, every ten years, an increase that is marked through- 

 out. As a result of this the quantity of sewage is steadily 

 increasing, and of course it is becoming more dilute. As 

 one would naturally expect, also, the quantity of storm 

 water is, in many parts of America, a far more important 

 one than it can ever be in this country. We are thus not 

 surprised to see that in Toronto, in 1891, gaugings in 

 different districts made over a period of three days gave 

 a discharge varying between fifty-three gallons per head 

 per diem to three hundred and sixteen gallons. The 

 author remarks that Mr. (jray, who gives these figures, 

 offers no explanation for the high average indicated by 

 this last figure. The very fact that we have these 

 differences, however, should render the book more 

 valuable to English engineers. The suggestions offered 

 in connection with the problem of dealing with these 

 enormous quantities of sewage, may afford hints for 

 dealing with the much smaller quantities that have to 

 be coped with on this side of the .-Xtlantic. 



DR. DREYER ON DARWINISM. 

 Peneroplis, cine Studie zur Biologischen Morphologic und 

 2ur Spccies-frage. Von F. Dreyer. Pp. ix -I- 119. 

 Plates V. (Leipzig: Engelmann, 1S98.) 



DR. DREYER'S work on Pcneroplis is of great 

 interest, not only because of the valuable observ- 

 ations which it contains, but as an indication of the way 

 in which an increasing number of German zoologists 

 regard the problem of animal evolution. 



The main part of the work is devoted to a description 

 of the form-varieties of shells of Pcneroplis, as seen in a 

 sample of sand from the shore of the Red Sea. The 

 description is illustrated by figures of more than two 

 hundred specimens, chosen as examples of the various 

 ways in which the "typical" spiral form may be de- 

 parted from. 



Dr. Dreyer has rightly called his essay "eine Studie 

 zur Species-frage " ; for there is no doubt that the con- 

 ception of a species, which is necessary in attempting to 

 deal with many problems of modern biology, must be 

 based on a knowledge of the whole series of varieties ex- 

 hibited by the species. .Vnd further, this knowledge must 

 be obtained in the way in which Dr. Dreyer has obtained 

 it, by the careful study of a large number of individuals, 

 taken in the first instance at random. Many of the dis- 

 torted ideas about animal variation which are evident in 

 writings on the subject arise from the belief that variation 

 can be profitably studied in museums, by comparing 

 "typical" specimens with the one or two striking devi- 

 ations from the type which the curator has chosen to ex- 

 hibit. There is, however, an additional element, essential 



