384 Proceedings of the Boyal Physical Society. 



end, so that the float does not begin to press on the lever 

 until it has risen through a distance corresponding to the 

 length of the slot. A similar slot is made where the rod E 

 is connected with the lever of the tap, and both these slots 

 are adjustable, so that at the time the arrangement over- 

 balances the tank is full, and the time has arrived for the 

 motor to be stopped. This was done gradually at first, but 

 it was found that with a rotary pump a time arrived when 

 the motor was working so slowly, that the pump had not 

 power enough to lift the water the required height, and thus 

 went on wasting power until the level of water in the fall- 

 tank had been sufficiently lowered to start the pump more 

 vigorously. To avoid this the present system was devised, 

 where, instead of having an arm with a weight like F directly 

 over the fulcrum of the lever C, a flat bar of iron, G, about 

 2 in. wide, is supported over C by two pillars. This bar is 

 turned up at both ends so as to prevent the rolling weight H 

 from falling off. The weight is made from a solid piece of iron, 

 and turned out in the middle so as to leave a flange hanging 

 over G on each side. For further safety a light rod, K, con- 

 nects the two ends of G, so as just to allow the weight to 

 pass under it, but sufficiently low not to allow it to leave its 

 place on the bar. It will be seen that as soon as ever the 

 lever C is in the slightest degree over the equilibrium, the 

 weight H runs along the bar G, with an increasing momentum, 

 and shuts or opens the tap instantly. This arrangement has 

 now been in work two years, and gives every satisfaction. 

 It is allowed to work day and night, and always stops or 

 starts the motor at the proper time. Care should be taken 

 to keep all the joints well greased, and the whole arrange- 

 ment should be galvanised so as to prevent rust. 



Next, as to the pump. As I said, I was at first supplied 

 with a rotary vulcanite pump by Messrs Leete, Edwards, and 

 Norman. This was kept in constant use for three years. 

 At first it worked fairly well, and required but little atten- 

 tion. As time went on, however, it proved less satisfactory. 

 I required continually the services of a mechanic, as the 

 rotating cups were frequently out of order — as they got worn 

 their distance apart had to be carefully regulated, or the 



