PERAMBULATOR, an instrument in general use for measuring distances on roads, for settling disputes concerning the charges of tbo drivers of hack.carriages, and for other purposes. It consists princi. pally of a wheel upon which it runs, and an index which shows the number of turns of such wheel reduced into miles, furlongs, poles, and yards.
The carriage or stock is made of wood, end is about 3 feet long. At one end is a handle far the person who uses it, and the other is fur. noshed with sockets in which the axle of the wheel turns ; this end of the stock has the centre part removed, by which are left two arms between which the wheel works. Upon the stock and just in front of the handle is the dial-plate, with Its two hands by which the distance is registered. The wheel Is 8 feet 3 inches, or pole, in circumference. Upon one end of the axis of this wheel is a small pinion, which works into a similar pinion at the end of a rod which passes up the stock or carriage to the works beneath the dial.plate. Motion is communicated by means of this rod to a worm or micrometer-screw, which turns once round for each revolution of the carriage-wheel of the perambu lator. This worm works into a wheel of 80 teeth, which is moved forward one tooth for every >5 pole, and carries a hand or index, which makes one revolution for 40 poles or one furlong. On the axis of this wheel is a pinion of 8 teeth, which works into a wheel of 40 teeth, and on the axis of this second wheel is a pinion of 10 teeth, which moves a wheel of 160 teeth. This hurt wheel carries another hand, which makes one revolution for 80 of the former. These hands are arranged in the same manner as the hour and minute hand of a watch, so that the three circles on the dial-plato are all concentric. The first of these circles is divided into 220, and the second into 40, the number of yards and poles contained in a furlong; the figures on these circles aro read off by the first-mentioned index, that which is attached to the wheel of 80 teeth. Tho third circle is divided into 80, the number of fur
longs in 10 miles, and to this circle belongs the index attached to the wheel of 160 teeth. The distance is ascertained by reading off the figures In the reverse order in which the circles are given above : divide the number on the first circle by 8, and you will have the dis tance required in miles, furlongs, poles, and yards.
The instrument is furnished with a atop or strap, so that after the distance is measured, the perambulator may be conveyed without the index being altered.
Unlike the pedometer, it requires no regulating, and the only risk of its giving the distance incorrectly, if' well constructed, is in passing over rugged and uneven roads, which will of course cause the index to show more than the true distance. In general, however, for short distances, this error is very trifling.
When about to commence a measurement, the wheel should be turned round until the first-mentioned index points to 220 on the circle of yards. Some are provided with a click and racket, by which this may be done with much less trouble than by the wheel.
There are other instruments for the same or similar purposes, bear ing different names, waywiser and odometer; but the construction of all of them is very similar.
Waywiser is the name generally given to that form of the instrument which is applied to a carriage, in which, by a slight adaptation to one of the wheels of the carriage, the instrument is made to register the number of turns of such wheel, in the same manner as the per ambulator.