The CHRONOGRAPH is undoubtedly the most perfect instrument yet invented for marking the exact time occupied by certain rapid movements or events or performances,--and is therefore well adapted for astronomical and medical observations, for timing machinery, for indicating the speed of a race, and of similar quick events even to the tenth of a second. It consists of an ordinary quick train lever movement on a scale sufficiently large to carry the hands for an 8-inch dial. The peculiar feature of the chronograph is its second hand, which is double, consisting of two distinct hands,--the one lying over the other. The lower of the two is furnished at the tip with a small reservoir having an extremely small orifice below; over this orifice the point of the upper hand is bent so as to fall exactly upon the puncture, and to convey through it, as with a pen, the ink held in the reservoir. The mode of operating with the chronograph at a race has been thus described. 'The chronograph is held firmly in the left hand of the operator, who watches the starters, but need not trouble himself to keep at the same time an eye upon the dial. At the moment of the start he presses the finger or thumb of his right hand gently upon the button of the pendant, and instantly a black dot is deposited on the dial, and--the operator being ready to touch the button at the precise moment of the finish, and thus to complete what we may call the chronogram of the event--the exact length of the race is registered, even to a decimal fraction of a second, and an indisputable record written by the instrument itself in black and white. The chronograph, it should be mentioned is, apart from its chronographic mechanism, an excellent time-keeper, and may be worn as an ordinary watch, being the same size as a gentleman's lever watch. REPEATING WATCHES are now made so as to require no key. They are constructed with a lever or chronometer escapement, and are known according to their method of repeating,--the ordinary _Repeater_ strikes the hours and quarters,--the _Half-quarter Repeater_ strikes the hours, quarters, and half-quarters,--the _Minute Repeater_ strikes hours, quarters, and minutes. The first tells the time in the dark or to the blind person to within a quarter of an hour, the second tells it within seven minutes and a half, the third tells it to the minute. The CLOCK WATCH and CLOCK REPEATING WATCH are also made so as to need no key. They strike the hours and quarters while being worn in the pocket, and have not only the two trains of wheels for going and striking as in a clock, but a third train provided for repeating purposes. Both mainsprings are wound up by the same winder by a forward and backward action of the pendant. They are constructed with either Lever, Duplex, or Chronometer Escapements, and some are provided with compensation balances adjusted to act equally at extremes of temperature.