Fuel, of course, is the source of the power. Furnaces which are capable of producing heat with the least consumption of fuel, tubes within the boilers that permit the freest possible contact of the heat produced and the water to be turned into steam, steam pipes that are flexible and yet strong, machinery that moves with the least friction in order to concentrate and utilise the power of the steam, and dynamos out of which electricity is evolved, together with auxiliary pumps and hoists and blowers and whatnot other devices to help create, control and economise the energy, are the essential parts of an electric power-plant. To insure economy and accuracy these are made as nearly automatic as possible.
At one end of the furnace house there is sunk in the cement floor a large iron scoop or tray into which cartloads of lump coal are dumped. This scoop-shaped receptacle is also the platform of a weighing machine so that each load is weighed. In the bottom of the scoop there is a trap-door, which, being opened, permits the coal to drop through between the teeth of a crusher where the large lumps are reduced, usually to the size of a small nut.
From the crusher the coal falls into the buckets of an endless chain-hoist and is conveyed aloft to great hopper-shaped bins which occupy the entire space under the roof over the furnaces. Leading back from each bin to the constantly moving grate bars of the furnace underneath is a pipe which delivers the crushed coal to the grate bars and distributes it evenly over their surface as fast as it can be received into the furnace, regulated, of course, by the consumption that is going on inside the furnace.
To accomplish this automatic feeding each set of grate bars is constructed in hinged sections, and forms a wide endless iron belt which revolves and carries the coal within the cavity of the furnace.
The coal crusher, bucket hoist, movable grate bars, ash collectors and sifters, pumps, blowers, lights and all other utilities of the plant, as well as the great travelling crane which can hoist and carry many tons' weight—any part of the enormous dynamos—from place to place, are operated by electricity which is generated in the dynamos.
Automatic gauges that measure and indicate, and switch-boards that regulate the energy created and stored in the dynamos play important parts in the economy and working of the plant and are analogous to appetite and taste in man.
ANALOGY ILLUSTRATED
The full analogy may be best illustrated by arranging the similar functions of the two energy-creating machines opposite each other in parallel columns.