There has recently been in progress at the Avon-mouth Docks, Bristol, an experimental demonstration of the possibilities of a new system of hydro-electrical power development by means of the head due to the tides, which in the estuary of the Severn are of the order of 30–40 ft. Hitherto, the economical development of tidal power on commercial lines has been beset by the difficulty of obtaining uninterrupted functioning of the generating machine. The turbines, requiring a minimum head or pressure for working purposes in the neighbourhood of 10 ft., are necessarily inoperative during such times as the difference between the level of the impounded water and that in the outer channel is less than this. The periods are considerable and may absorb a third of the tidal time. The difficulty can be overcome by a complex system of auxiliary basins or reservoirs, but the cost of these is generally prohibitive. Under the new system, which is due to Mr. Paul Shishkoff and is being exploited by Hydro-Thermal Power Ltd., of Westminster, a portion of the power produced by the turbines under tidal action is converted into heat by means of a water friction brake, the heated water being stored under pressure in a steam accumulator. When the tidal head falls below the minimum required to drive the water turbine, power is generated by a turbo-alternator driven by steam from the accumulator. In this way the intermissions of tidal force are bridged over. The power system is, of course, of a dual nature, being partly by water and partly by steam, but it has the merit of being self-contained and is, indeed, quite simple in design. The experimental plant at Avonmouth is only of small calibre, with an ordinary continuous load of 16 kw. and a peak load of 32 kw., but its successful operation opens out a wide field of possible development for the Shishkoff system.