If we can procure a battery in which we may store energy, which shall always be on draught by merely pushing a button, one which "is not injured by overcharging nor too rapid discharging, nor even by complete discharge"; one which is not injured by standing idle for any length of time, either charged or discharged; and finally one which "is practically foolproof"--we want to try it. I propose that you appoint a committee to look into it. But at any rate this enterprise must go on even if I have to hire a man to live in the loft of the mill and keep the machinery going. [Illustration: Fig. 141] "No man in the loft," said Dyne, "while I have my rations." "There will be no need for him so long as I can store energy here," said Erg, "so let the job of equipping the establishment go on in the regular fashion." After a long confab one evening at the mill we settled upon the arrangement shown in Fig. 141. _D_ represents the location of the doors and _W_ that of the windows. The equipment is designated as follows: _A_, saw; _B_, planer; _C_, lathe; _E_, emery wheel; _F_, grindstone; _G_, dynamo; _H_, forge; _I_, storage battery; _J_, switchboard; _K_ and _L_, counter shafts suspended from the ceiling. The water-wheel is belted directly to the counter shaft _L_. This revolves at the rate of 240 r. p. m. A two-foot pulley on this shaft is belted to a one-foot pulley on the dynamo _G_, giving the dynamo a speed of 480. A 4-inch pulley on this counter shaft is belted to a 16-inch pulley on the grindstone _F_, giving the stone a speed of 60 r. p. m., or one revolution per second. A 32-inch pulley on shaft _L_ is belted to an 8-inch pulley on the counter shaft _K_, giving a speed of 4 times 240, or 960 r. p. m. 12-inch pulleys on this shaft are belted to 6-inch pulleys on each of the machines _A_, _B_, and _C_, giving them a speed of 1920 r. p. m., and a 16-inch pulley on this shaft is belted to a 4-inch pulley on the emery wheel, giving it a speed of 3840 r. p. m. As soon as everything was in running order, Harold took his mother down to the machine shop and started all the machinery going at once, and while they stood in the middle of the room I heard him explaining to her how she might find out the speed of each machine. He said that she must start with the grindstone, because that goes slowly enough to count. She held her watch in hand and counted the number of revolutions in a minute, as he directed, and found them to be sixty. Then he asked her to judge how much larger the pulley on the grindstone was than the corresponding one on the counter shaft. She said that she thought it looked four times as large. He told her that she had it just right, and explained that the shaft must move four times as fast as the stone, or 240. "Now how fast do you think the emery wheel is going?" She acknowledged that she had no idea. "Well," said he, "when you get real used to it you can tell by the tone a wheel makes just about how fast it is going."