PERAMBULATOR, is an instrument for measuring distances on roads. It consists principally of a wheel upon which it runs, ana. an index which shows the number of turns of the wheel reduced into miles, furlongs, poles, and yards. The carriage or stock, which is divided in order to receive th3 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 wheels turns. 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 81 feet, or pole, in circumference; and upon one end of its axis is a small pinion, which works into a similar pinion at the end of a rod pass ing up the stock or carriage to the works beneath the dial-plate. Motion is commu nicated by means of this rod to a worm or micrometer-screw, which turns once round for each revolution of the carriage-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 carves another hand, which makes one revolution for 80 of the former, that is for ten miles. The move ments of the two index-hands thus shew the miles and furlongs passed over.
There are other instruments for the same or similar purposes, bearing different names, as Wayuri,ser and Odometer ; but the con struction of all of them is very similar. Way wiser 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.