The electric boats work on a similar principle. One pool, 180 feet long, has thirty boats, each containing an electric motor of 6-1/4 horse-power and running at 1,200 revolutions a minute, fitted in the same way as an inboard petrol motor for small boats. A forward or reverse movement is effected simply by giving the steering wheel one complete turn. The boats, which travel at about six miles an hour, cannot capsize. Contrary to past practice, the power does not come from overhead wire netting earthed to the water. The process is reversed. The wire netting is the negative pole and the system is thus made safer than ever. Spectators can stand round the pool, placing their hands in the water, and feel nothing. Fresh water is used with four tons of salt dissolved in it.
The electric apparatus is larger than might be suspected. A three-phase rectifier and transformer convert 400 volts alternating current to 100 volts direct current, there being two valves to each phase. On some outdoor pools, however, petrol motors are used.