The American Cyclopædia (1879)/Odometer
ODOMETER (Gr. ὁδός, a road, and μέτρον, a measure), an instrument for determining the distances passed over in travelling, also known as pedometer, perambulator, &c. Odometers attached to the wheels of carriages were employed by the ancient Romans. This kind of odometer records by a mechanical contrivance the number of revolutions of a wheel in passing from one place to another. The odometer carried by pedestrians, and designed for recording the number of steps, is generally called a pedometer. It resembles a watch in size and shape, and may be worn in the vest pocket. Its machinery is so constructed that by the rising and sinking of the body with each step a lever is made to vibrate, which moves the index hand connected with it.