86 

Local and Municipal Authorities. By Dr. S. 
Rideal and Dr. E. K. Rideal. Pp. xii+274. 
(London: Crosby Lockwood and Son, 1914.) 
Price 7s: 6d. net. 
HESE two books to some extent supplement 
one another, the former dealing with the 
analysis of water (among other things), while the 
latter treats mainly with the production of a pure 
and wholesome water supply; the one being de- 
signed ‘for the analyst and public-health student, 
the other for local and municipal authorities. 
(1) The volume by Messrs. Purvis and Hodgson, 
as its name implies, deals primarily with the 
chemical analysis of water, sewage and foods, and 
such allied subjects as the detection and estima- 
tion of preservatives, and the analysis of air, coal- 
gas and other gases, rag flock, and urine. 
The opening chapter, which is by far the longest 
in the book, deals with the analysis of water, 
sewage, and sewage effluents. More or less de- 
tailed descriptions are given of the chief tests em- 
plcyed, and in this connection one might note the 
desirability of the standardisation of some of these 
tests, notably those for albuminoid ammonia, and 
oxygen absorbed from permanganate. Some of 
the tests, as described, do not appear to be capable 
of any great delicacy. This is particularly the 
case with the ammonia tests, which apparently 
are about ten times less delicate than those em- 
ployed in the laboratories either of the Metro- 
politan Water Board or the Royal Commission on 
Sewage Disposal. 
At the conclusion of the chapter the results of 
a series of investigations, chiefly by Mr. Purvis, 
are given dealing with the effect of mixing sewage 
with river water and sea water. Much of the 
work is obviously inspired by the eighth report 
of the Royal Commission on Sewage Disposal. 
The researches have resulted in some interesting 
information, but the manner in which the results 
are presented makes a full appreciation of them 
very difficult, and some of the results of an in- 
vestigation of the changes which occur to a 
mixture of sewage and sea water in course of 
time show such wide variations that one is inclined 
almost to doubt the accuracy of some of the 
figures; for example, the albuminoid ammonia of 
a mixture of sewage and sea water analysed after 
115, 165, and 176 days is given as 0078, 0'002, 
and o'13 respectively (Table F1, p. 74). 
The remaining chapters of the book consist of 
instructions for carrying out the analyses of the 
other substances mentioned above. The instruc- 
tions are usually remarkably clear and concise, but 
occasionally they become much involved and even 
ungrammatical, suggesting that these parts have 
been hurriedly compiled. This, however, is a 
NO. 2369, VOL. 95] 
“NATURE 



[Marcu 25, 1915 

small blemish, and can easily be corrected in a 
future edition; it in no way detracts from a 
book which will undoubtedly be of great value 
both to the analyst and the student in a public- 
health laboratory. 
(2) The second volume under review deals with 
the question of water supply in its widest sense, 
and only touches on the subject of analysis in the 
last chapter, and then more on the interpretation 
of the results than on the way these results are 
obtained. 
The opening chapters deal with the inorganic 
and organic contents of natural waters, both — 
useful (as in medicinal springs) and harmful (as 
in water from polluted sources), mention being 
also made of some of the living contents, par- 
ticularly those grouped under the name of 
plankton. Following this preliminary matter, the 
book deals with the successive stages in water 
supply under the headings of sources of supply, 
distribution, storage, filtration, softening, sterilisa- 
tion, and finally the analysis of water and inter- 
pretation of results. 
There is so much of interest in this valuable 
book that it is difficult, in the space allotted, to 
more than mention many of the important subjects 
dealt with, but several points call for especial 
notice. : 
The chapter devoted to storage is full of interest- 
ing information, particularly with regard to the 
physical, chemical, and bacteriological changes 
which occur in water subjected to storage. It is 
pointed out, for instance, that while the changes 
which occur to an initially impure water are 
wholly or mainly in the direction of improvement, 
an initially pure water may considerably deteri- 
orate owing to prolonged storage. 
Before going into the important subject of 
filtration, the authors devote a chapter to pre- 
liminary purification, including precipitation and 
assisted sedimentation, deferrisation, and the 
abatement of nuisances arising from living 
growths in the reservoirs; this subject is treated 
very fully, and reference is made to the work of 
many investigators both English and foreign. 
Chapters vii. and viii. deal in great detail with 
the question of sand filtration and mechanical 
filtration, chapter ix. with softening, and then 
follow two important chapters on sterilisation. 
The authors enter a strong plea for the sterilisa- 
_tion of all supplies from polluted or pollutable 
sources. Against the contention that the expense 
of sterilising is prohibitive in a great many cases, 
the suggestion is put forward that there might be 
a dual supply for drinking and non-potable pur- 
poses, but the arguments in favour of this course 
do not seem to be very convincing; moreover, the 
