In this class of appliances may be included the measuring-wheel or " circumferentor," employed for measuring the periphery of a carriage wheel to find the length of tire required. It consists of a small wheel of known circumference graduated on its peripheral edge and in a stock or holder. The zero mark of the measuring-wheel is placed at a marked spot on the carriage-wheel, around which it is caused to travel; the number of revolutions of the small wheel and such a fraction of a revolution as there may be, indicate the perimeter of the carriage-wheel. Of more complicated construction is the " lumber-measurer," by which the number of superficial feet contained in boards of different lengths can be estimated. Within a case in a vertical position is a toothed disc, which, by being made to pass along the surface of the lumber, actuates a mech anism that indicates on a dial the superficial contents. Projecting from the bottom of the case and terminating under the centre of the disc, is a sleeve which enables the operator to begin measuring with the edge of a board directly under the centre of the disc.
pedometer is an apparatus for registering the number of steps taken by a pedestrian and for ascertaining the distance lie travels. In exterior appearance the pedometer resembles a watch, and may be car ded in the watch-pocket, or may be hung on a belt, or secured to a button hole. The pedometer has a dial, and a hand which is so counterweighted
that at each motion of the person in walking the weight pulsates and advances the hand one degree. It requires no winding, but begins its ope ration as soon as the wearer takes a step, and quickens, moderates, stops, or resumes its work exactly as the wearer steps, without requiring the slight est attention or imposing on the pedestrian a special or non-interrupted gait; it not only indicates long distances, but also adds up short distances made at different times, and shows the exact total. To simplify the reck oning, the dial is usually divided into twelve spaces, each space represent ing one mile; but after having marked that distance the hand continues moving around the dial. To ascertain if the instrument is regulated correctly, it is necessary for the wearer to walk over a certain distance— a mile, for example. If the hand has marked one division, the pedometer is correct; if the hand :narks less or more than one division, the instrument can be regulated by means of a screw, which is turned to the right or to the left respectively.