PERAMBULATOR is an instrument for taeasuring distances on roads. It con sits principally of a wheel, upon which it runs, and an index which shows the num ber of turns of the wheel reduced into miles, furlongs, poles, or yards. The carriage or stock, which is divided in or der to receive the wheel, is made of wood, and is about three feet long. At one end is a handle for the person who uses it, and the other is furnished with sockets, in which the axle of the wheel turns. Upon the stock, and just in front of the handle, is the dial-plate, with its two hands by which the distance is re gistered. wheel is 8+ feet, or pole in circumference ; and upon one end of its axis is a small pinion which works in to a similar pinion at the end of a rod passing 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 car riage-wheel of the perambulator. This
worm works into a wheel of 80 teeth, which is moved forward one tooth for every 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 moves a wheel of 160 teeth. This last wheel car ries another band, which makes, one re volution for 80 of the former, that is, for ten miles. The movements of the two index hands thus show the miles and fur longs passed over.
'There are other instruments for the same or similar purposes, bearing differ ent names, as Warmer and Odometer, but the construction of all of them is very similar. Waywiser is the name gener ally 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 perambulator.