_Dynamo Running as Motor_ _Horse-power Hours_ _Dr._ _Cr._ To energy impressed by battery 48 By energy delivered back to water-wheel 36 By loss in heat 12 --------- 48 48 (This dynamo being a particularly inefficient motor.) We cannot give the account of a water-wheel acting as a pump, because such a machine has not yet been perfected. It is evident however that if a water-wheel could be devised that should be a perfect pump, the losses in this chain of machinery are more than half; indeed, the accounts show them to be 60 per cent. We should, therefore, be able to return less than half the water drawn from the lake each day, and we should rapidly move toward bankruptcy. "Well," said Ernest, "my proposition is more successful than that, because it sets out to be a fool proposition." It was first suggested by the snake who undertook to swallow himself. Suppose the account does taper down from eighty to one, so does the snake, but he still remains "wise as a serpent." Our account would stand as follows: _Dynamo_ _Battery_ _Motors_ 36 27 27 20 20 15 15 12 12 9 9 7 7 5 5 4 4 3 3 2 2 1 1 .8 .8 .6 .6 .48 .48 .36 .36 .27 .27 .20 .20 .15 .15 .12 .12 .09 .09 .07 .07 .05 .05 .04 .04 .03 .03 .02 .02 .01 .01 .003 It is evident that while our energy would dwindle continually we should never quite come out of the little end of the horn, since any number may diminish by 20 per cent. of itself indefinitely. "Let us get at something practical," said Erg. "How are we going to furnish electricity to the cottage when the dynamo is not running? If we put a storage battery at the cottage, how are we going to store it having nothing but alternating current up there; and if we attempt to transmit current from our central station battery, how are we going to get along with the drop in the voltage?" "I'll tell you how to do that," said Dyne. "They want 20 amperes and the line offers 4 ohms of resistance. That means a drop of 80 volts. We have simply to provide a subsidiary battery of 48 cells, which we may throw in series with our 57 cells when we supply electricity to the cottage, and then they will have the right voltage for use out there."