APRIL 9, 1914] 
NALURE 
135 
WATER, SUPPLIES. 
(1) Studies in Water Supply. By Dr. A. C. 
Houston. Pp. xii+203. Macmillan’s Science 
Monographs. (London: Macmillan and Co., 
Etd., 1913.) Price 5s. net. 
(2) Water: its Purification and Use in the Indus- 
inves. By W. W. Christie. Pp. xi+ 2109. 
(London: Constable and Co., Ltd., 1913.) Price 
8s. 6d. net, 
(1) R. HOUSTON has gathered together an 
epitome of his own researches, which 
have been scattered among a considerable number 
of reports and papers. In the first chapter, which 
deals with sources of water-supply, he directs 
attention to the remarkably low death-rate from 
typhoid fever in London during the past few 
years, a rate which in the year 1911 amounted to 
only 003 per thousand of the population. After 
discussing the rivers Thames and Lea as sources 
of water-supply, he proceeds in subsequent chap- 
ters to give results of his observations upon the 
purification of water, finally concluding the volume 
by a discussion and description of the methods 
carried out under his direction in the laboratories 
of the Metropolitan Water Board. 
The main conclusions which Dr. Houston draws 
from a large amount of experimental work may 
be summarised as follows :—River water exposed 
to manifold pollutions, and furnishing ample 
chemical and bacteriological evidence of objection- 
able contamination, may fail to show any or 
scarcely any of the microbes of water-borne dis- | 
ease; and he raises the question as to whether 
we have not exaggerated the value, high as it is, 
of the sand filter as a factor in our long-continued 
immunity from typhoid fever, and whether some 
at least of this freedom may not be due to the 
fact that the water was not primarily so noxious 
as it has hitherto been regarded. He is convinced 
that artificially-added typhoid bacilli die fairly 
rapidly in stored water, even when such water is 
of great initial impurity, and that a preliminary 
storage of water is an important factor of safety. 
This purification of water under storage conditions 
is chiefly due to the sedimentation, equalisation, 
and devitalisation of microbes; and he shows that 
by the second week the reduction in the artificially 
cultivated typhoid bacilli added to river water is 
more than 99 per cent. on the average, and that 
storage reduces the number of bacteria of all sorts 
and devitalises the survivors, if sufficiently pro- 
longed. 
Taking the chemical and bacteriological results 
together, Dr. Houston demonstrates that the 
beneficial effect observed in connection with simple 
continuous flow settlement of water may be con- 
siderably enhanced by the use of coagulants, such 
NO. 2319, VOL. 93| 
as aluminoferric, ete. He finds that when a hard 
water is overdosed with lime a considerable bac- 
tericidal effect is produced; and if after a suitable 
interval sufficient untreated water is added. to 
combine with the excess of lime, a much safer 
water for drinking purposes is obtained. Speak- 
ing generally, these experiments demonstrate that 
the bactericidal dose of lime for hard waters would 
appear to be rather less than 1 to 5000, and with 
very soft waters 1 to 50,000. This method is 
especially attractive in cases where a water, bac- 
teriologically impure, has in. any event to be 
softened, and where a contaminated river supply 
has scarcely any available storage accommodation 
prior to sand filtration. 
The author is to be congratulated, not only 
upon the good work to which the volume bears 
testimony, but also upon bringing it together in 
this monograph, and presenting it in a condensed 
and readable form. 
(2) Mr. Christie’s small work is mainly composed 
of a series of articles which appeared in “Indus- 
trial Engineering and Engineering Digest” for 
1910-1911, and it is to be commended more parti- 
cularly for its treatment of the use of water in 
various branches of industry. While much useful 
information is given upon the subject of the puri- 
fication of water which would fit it for drinking 
purposes, this portion of the book is less satis- 
factorily dealt with than that which is concerned 
with the use of water for industrial purposes. 
Indeed, the treatment of the sources of water, its 
analysis and standards of purity, is fragmentary 
and unsatisfactory. It is impossible to deal with 
the subject of the standards of purity of water 
except in regard to the sources from which ‘the 
water is derived. More particularly is this neces- 
sary with reference to chlorine standards; and the 
standard given for chlorine in water, of from 
3 to 10 parts in a million, is useless and mislead- 
ing. Extremely few of the drinking water sup- 
plies of this country would conform to such a 
standard. The chapters on water softening, pres- 
sure filters, oil filters, and boiler waters are the 
best contributions to a work which is exceedingly 
well produced, the illustrations being a noteworthy 
feature of the publication. 
DUR BOOKSHELF. 
From the Letter-Files of S. W. Johnson. 
by his Daughter, Elizabeth A. Osborne. 
Edited 
Pp: 
292. (New Haven: Yale University Press; 
London: Oxford University Press, 1913.) 
Price tos. Gd. .met. 
No teacher of agricultural chemistry can afford 
to do without Johnson’s two books, ‘ How Crops 
Grow,” and ‘How Crops Feed.” - If he tries it, 
