THE TURNING-ON OF AN ELECTRIC LAMP IN THE HOUSE.
Everyone knows that when a spigot connected with one of the water faucets in a house is turned, as, for example, the spigot, at the wash-stand, the water runs out of the pipe, at the faucet, and will continue running out as long as the spigot is left open. When the spigot is opened, we say that the water is turned on; when it is closed, we say that the water is turned off.
The water flows out of the pipe, as soon as an opening is made by the turning of "the spigot" because the water is constantly pressing against the inside of the pipe. When no opening exists, the water simply presses against the pipe, but does not run out until an opening is made.
We can both see and feel the water running out of the pipe. We can fill a tumbler or other vessel with the water; we can drink the water, or can use it for washing, cooking and other well-known purposes. We introduce water into the house in order to make use of it for the many purposes for which it is adapted.
Every one, too, knows that when we turn the key connected with an incandescent electric lamp incandescent electric lamp, the lamp glows, or throws out light, and will continue throwing out light as long as the electricity continues to flow through the filament. When the key is again turned, the electric flow, or current, is stopped, and the lamp ceases to throw out light. The lamp glows, or throws out light, because electricity flows from the wires through the slender carbon thread or filament. When the key is turned along the lamp, so as to permit the electricity to flow, we say that the electricity is turned on; when the key is turned across the lamp, so as to prevent the electricity from flowing, we say that the electricity is turned off....