TIDAL POWER. 
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Tidal Power. a: 
- The idea of utilizing the rise and fall of the tides for power purposes 
has long been a favorite one. Up to the present, however, no power 
development of this kind, of any appreciable size, has been carried out. © 
The comparatively recent arousing of interest in water-power develop- 
ment in general, and the great advance .in the cost of fuel, have been 
accompanied by a corresponding interest in tidal-power schemes, an 
their commercial possibility is at the moment the subject of serious 
investigation in this country and in France. 
The power which may be developed from a tidal basin of given area 
depends on the square of the tidal range, and since the cost per horse- 
power of the necessary turbines and generating machinery increases 
rapidly as the working head is diminished, the cost per horse-power of 
a tidal-power installation, other things being equal, will be smallest 
where the tidal range is greatest. It is for this reason that the western, 
and especially the south-western, coasts of Great Britain, and the 
western coast of France, are particularly well adapted for such develop- 
ments, since the tidal range here is greater than in any other part of the , 
world, with the possible exception of the Bay of Fundy, Hudson’s Bay, 
and Port Gallelos, in Patagonia. aay 
In Great Britain the highest tides are found in the estuary of the | 
Severn, the mean range of the spring tides at Chepstow being 42. feet, 
and of the neap tides 21 feet. In France the maximum range occurs at 
St. Malo, where it amounts: to 42.5 feet at spring tides, and about 
18 feet at neap tides. The tidal range in the Dee is 26 feet at springs, 
and 12 feet at neaps, while the mean range of spring tides around the 
coast of Great Britain is 16.4 feet, and of neap tides 8.6 feet. 
Many schemes of tidal-power development have been suggested 
from time to time. ‘Briefly outlined, the more promising of these are as 
follows :-— ; “0 
(a) A single tidal basin is used, divided from the sea by a dam or 
barrage, in which are placed the turbines. The hasin is filled through 
sluices during the rising tide. At high tide the sluices are closed. 
When the tide has fallen through a height the magnitude of which 
Fig A 
depends on the working head to be adopted, the turbine-gates are opened, 
and the turbines operate on a more or less constant head until low tide. 
The maximum output from a given area of basin is obtained when the 
*Reprinted from Nature, No..2640, Vol. 105. ‘ : Pare 
501 
