122 SECTIONAL ADDRESSES. 
of eight hours daily throughout the year, would be of the order of 
450,000 horse-power. 
Many suggestions for utilising the tides by the use of current 
motors, float-operated air compressors, and the like have been made, 
but the only practicable means of utilising tidal energy on any large 
scale would appear to involve the provision of one or more dams, 
impounding the water in tidal basins, and the use of the impounded 
water to drive turbines. 
The energy thus rendered available is, however, intermittent; the 
average working head is low and varies daily within very wide limits, 
while the maximum daily output varies widely as between spring and 
neap tides. 
If some electro-chemical or electro-physical process were available, 
capable of utilising an intermittent energy supply subject to variations 
of this kind, the value of tidal power would be greatly increased. At 
the moment, however, no such process is commercially available, and 
in order to utilise any isolated tidal scheme for normal industrial 
application it is necessary to provide means for converting the variable 
output into a continuous supply constant throughout the normal 
working period. 
Various schemes have been suggested for obtaining a continuous 
output by the co-ordinated operation of two or more tidal basins 
separated from each other and from the sea by dams with appropriate 
sluice gates. This method, however, can only get over the difficulty 
of equalising the outputs of spring and neap tides if it be arranged that 
the maximum rate of output is that governed by the working head at 
the lowest neap tide, in which case only a small fraction of the available 
energy is utilised. 
When a single tidal basin is used it is necessary to provide some 
storage system to absorb a portion of the energy during the daily and 
fortnightly periods of maximum output, and for this purpose the most 
promising method at the moment appears to involve the use of an 
auxiliary high-level reservoir into which water is pumped when excess 
energy is available, to be used to drive secondary turbines as required. 
It is, however, possible that better methods may be devised. Storage by 
the use of electrically heated boilers has been suggested, and the whole 
field of storage is one which would probably well repay investigation. 
If a sufficiently extensive electrical network were available, linking 
up a number of large steam and inland water-power stations, a tidal- 
power scheme might readily be connected into such a network without 
any storage being necessary, and this would appear to be a possibility 
which should not be overlooked in the case of our own country. 
Investigation necessary.—A tidal-power project on any large scale 
involves a number of special problems for the satisfactory solution of 
which our present data are inadequate. 
Thus the effect of a barrage on the silting of a large estuary, and 
the exact effect on the level in the estuary and in the tidal basin at 
any given time, can only be determined by experiment, either on a small 
installation, or preferably on a model of the large scheme. 
Many of the hydraulic, mechanical, and electrical problems involved 
