JULY ToS | 
NATURE 
477 

guish on the map of Europe between major and 
minor industrial areas, and the absence of large- 
| ment upon the subject. 
scale economic maps of the countries of Europe | 
distinctly handicaps the atlas for purposes of ad- 
vanced study. 
Prof. Lyde has also contributed an introduction, 
which contains a large amount of both informa- 
tion and speculation. The prefixing of a lengthy 
and highly didactic introduction to an atlas in- 
tended for general university use is a somewhat 
new departure from well-established precedent. 
The presence of such an introduction tends to 
embarrass the teacher, who in this case may pos- 
sibly differ from Prof. Lyde both in matters of 
opinion and in methods of teaching. A _ brief 
description of the plates of an atlas may at times 
be useful, but the proper place for all contro- 
versial matter is in an accompanying handbook 
which need not necessarily be placed by the 
teacher in the hands of his students. An atlas 
should be concerned solely with facts, to the 
ultimate arbitrament of which a teacher may refer 
all matters of opinion. 
There are two methods of teaching economic 
geography as a university subject. One is to 
make certain general statements, and then to 
proceed to illustrate them by reference to the dis- 
tribution of certain commodities and industries. 
The other is to begin with the distribution, and 
after due consideration of all the facts to attempt 
a theoretical explanation. Since many of the so- 
called principles of economic and anthropo-geo- 
graphy are by no means demonstrated, the latter 
method would at present appear to be preferable. 
Prof. Lyde, however, evidently believes that 
better results may be obtained from the former. 
Hence his introduction abounds in picturesque 
and suggestive ideas which the student is encour- 
aged to believe may be verified by a careful ex- 
amination of the facts of production and distri- 
bution. For example, it is stated that the ideal 
climate for wheat is of the Mediterranean type, 
while as a matter of fact the maximum yield per 
acre, which, in the absence of any other universal 
criterion, may fairly be taken as an indication 
of climatic suitability, is found in a region the 
climate of whichis not usually classified as Medi- 
terranean. 
Again, the climatic control of the distribution 
of textile industries, emphasised in the introduc- 
tion, has long been one of the pious beliefs of 
economic geographers. It has now become cus- 
tomary to limit the application of this so-called 
principle to the manufacture of only the finest 
goods, but the necessity of introducing such a 
limitation should be sufficient to put teachers on 
their guard against making any categorical state- 
NO. 2383, VOL. 95] 
To state in advance and 
with authority the conclusion which should be 
drawn from a study of certain regional and econo- 
mic facts is an insidious method of giving what 
| may be an unfortunate bias to the undeveloped 

mind. 
To. she 
SEWAGE PROBLEMS. 
Sewage Purification and Disposal. By G. B. 
Kershaw. Pp. x+340. (Cambridge: At the 
University Press, 1915.) Price 12s. net. 
HOSE who accept the conclusion of the 
author that “Sewage purification is the 
outcome of the activities of bacteria mainly, but 
assisted by chemical and physical actions, and the 
purifying agencies of various alge and water 
plants,” will probably consider that only in a 
limited degree does this book fulfil the claim of 
the editors of the series to present the latest 
scientific and practical information upon the sub- 
ject with which it deals. 
Consideration of the biological aspect of the 
problem is comparatively brief and superficial, 
and the author is of opinion that “It does not 
come within the province of this book to touch 
more than briefly upon chemical points.” The 
outlook is that of an engineer, with extensive 
rather than intensive experience of the problem; 
the treatment descriptive and intelligently em- 
pirical rather than scientific, but within these 
limits the book informative account of 
present-day practice. 
The difficulties, both quantitative and qualita- 
tive, of the sludge problem are kept well before 
the reader’s attention, and it is realised that cir- 
cumstances may justify the discharge of appre- 
ciable quantities of suspended matter on to suit- 
ably designed filters, with the view of effecting 
the separation of a large proportion of the in- 
evitable solid matter in its least objectionable 
form. The entire failure to recognise the sig- 
nificance of the Dibdin slate bed, in this con- 
1Seeatl 
‘nection, is somewhat remarkable. 
Probably the most useful sections of the book 
are those dealing with conservancy systems, and 
with land treatment, in both of which a clear 
conception of actualities is presented. 
The references to foreign practice constitute a 
valuable feature, and in certain sections, as, for 
instance, those dealing with the influence of tank 
velocity upon the character of the deposit, either 
of detritus or of the main bulk of sludge, might 
with advantage have been extended, since English 
practice, as interpreted by the author (in dealing 
with the construction of detritus tanks, for ex- 
ample, “from 1/1ooth to 1/200th part of the total 
