526 
which experience has dictated. All flowing water 
moves under the guidance of natural laws which 
produce in their combinations complex results, 
which must be taken into consideration fully if 
favourable results are to be obtained from the 
regulation of river channels. 
One subject dealt with at some length which 
deserves the careful attention of river engineers 
is the prevention of floods by regulating the flow 
of the water by means of natural or artificial reser- 
yoirs. It is not for want of example that this 
important subject has not received the attention 
that it deserves. So long ago as the time of 
the Pharaohs, the regulation of the Nile was 
effected by the construction of Lake Meeris. 
Advantage was taken of a large natural depression 
near the river, covering an area of 695 sq. miles. 
This was embanked, and a channel cut connecting 
the lake and the river. In times of extraordinary 
high Nile, an opening was cut in the embankment 
and the water from the river allowed to flow 
through the cut to the artificial lake ; when the flood 
subsided the cut in the bank was made up again. 
In America the great lakes form a_ practical 
object-lesson as to the use of storage reservoirs. 
These operate to preserve a balance between the 
cycles of wet and dry seasons, and so regulate 
the depth of the water in the rivers with which 
they are connected, to the advantage of navigation 
in dry seasons, and the prevention of floods when 
the rainfall is excessive. 
The largest artificial reservoir that has been 
constructed in the United States is that at the 
head of the Mississippi. The country in the 
neighbourhood of the source of this river is inter- 
spersed with a great number of small lakes and 
depressions. About thirty years ago, following 
the Egyptian example, embankments were con- 
structed to hold up the water over this area in 
wet seasons, and works carried out to enable this 
to flow out when the river could take it without 
causing floods. In Italy the lakes adjacent to the 
northern tributaries of the Po have in like manner 
been adapted to serve the same purpose. The 
flow of the Rhine in its upper part is also regulated 
by the lakes with which it is connected. 
One of the most extensive modern artificial 
systems of regulation is to be found in Russia, at 
the head waters of the Volga and Msta rivers, 
where, by the embankment of a large tract of low 
swampy land, the flow of water in the Volga has 
been so regulated that the length of time over 
which navigation is practicable in dry seasons has 
been increased by three months. 
The most recent example of river regulation in 
Europe has been carried out in Silesia, where, on 
an average, the river Oder overflowed its banks 
NO. 2306, VOL. 92] 
NATURE 
[January 8, 1914 
and flooded the country through which it flows 
once in eight years. The loss to the inhabit- 
ants caused by the last of these floods was estim- 
ated at half a million pounds. The scheme adopted ~ 
has been to form a series of reservoirs by con- 
structing embankments across the valley and hold- 
ing up the water when the river is not able to 
carry off the rainfall. 
OUR BOOKSHELF. 
The Wonders of Wireless Telegraphy. By Prot. — 
J. A. Fleming, F.R.S. Pp. xi+279. (London : 
S.P.C.K., 1913.) Price 3s. 6d. “net. 
Dr. FLEMING’s reputation as inventor, experi- 
menter, theorist, and expositor in the domain of 
wireless telegraphy is so high that any work by 
him upon this fascinating and difficult subject 
will be welcome. We already have learned to 
look to his advanced and mathematical works for 
guidance when seeking to understand the intrica- 
cies of spark or ethereal telegraphy. In the pre- — 
sent book, however, Dr. Fleming has undertaken 
a task which in many ways is more difficult than — 
writing an advanced treatise, for he has attempted, 
and his success is great, to unfold the nature of 
the operaticns on which this new art depends 
without the use of mathematical or very technical 
language. This book is to be considered as a con~ 
tinuation of, or addition to, “ Waves and Ripples 
in Water, Air, and A®ther,” by the same author. 
Without following the treatment of the several 
chapters, special reference may be made to the 
fifth chapter, which is of particular interest, as we 
there find the most recent views on long-distance 
transmission as not affected by the curvature of 
the earth, but susceptible to peculiarities of 
weather, and, ‘above all, to the effect of the rising’ 
or setting sun. Another feature is the discussion. 
of the methods of transmission by intermittent 
spark, continuously existing are, and various 
mechanical methods of obtaining continuous waves 
or nearly so, and this it would appear might be 
read to advantage by some whose knowledge of 
electrodynamics is greater than their familiarity 
with the everyday difficulties met with in working” 
commercially. : 
The chapter on the wireless telephone is also 
one which will appeal to every reader. : 
a 
(1) Who’s Who, 1914. Price 
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(3) The Englishwoman's Year-Book and Directory, 
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(1) THe best praise which can be given to th 
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