Page:Popular Science Monthly Volume 29.djvu/201

Rh itself turns a small pinion that carries the "fly-fan." The use of the fan is to keep an even motion. The large wheel that we have spoken of turns once at every stroke of the bell. In Fig. 5, a wire, c, runs over to the center wheel, D. In Fig. 3, a pin on the center wheel pushes up this wire when the clock is ready to strike. If the end of the wire (in Fig. 5) rests at the four notches, it shows that four o'clock



has been struck. If the center wheel pushes the wire up again, or pulls it out from the notch where it is resting, the large wheels at B are released; the weight commences to turn A and B, and the pins in A set the hammer c to striking the bell d. It keeps on striking until five has been struck. The wire then drops into a notch and holds the striking-wheel fast until the center wheel moves the wire again—thus saying that it is time to strike six. The wheels then turn again until the wire comes down and stops them. Alarm-clocks have an arrangement by which the spring that sounds the alarm is let loose at the hour when the owner wishes to be awakened.

The boys who went to school in New England sixty years ago had no such device to waken them in cold winter mornings as the modern alarm-clock; they had to waken each other, in order to have a good start in kindling their fires, so that they could enjoy an hour's hard study, and sometimes a recitation, before breakfast.