174 Performance of Some Timekeepers. 



balance spring that, notwithstanding the presence of the 

 fusee to equalise the action of the motive power, which is 

 absolutely necessary with this escapement, it is a very poor 

 timekeeper. Sully, a celebrated English watchmaker of the 

 last century, found that in the verge watches of his day an 

 increase of one-half in the motive power caused a variation 

 of six hours a day. Captain Cuttle's watch, immortalised 

 by Dickens, had undoubtedly a verge escapement. 



The duplex escapement derives its name from the double 

 set of teeth on the scape wheel — a short set to give the 

 impulse to the balance, and a long set to keep the train at 

 rest, except at the moment of escape. It was invented near 

 the end of the seventeenth century. Its inventor is not 

 known with certainty. It was claimed, however, by the 

 celebrated Robert Hooke, the contemporary, and in some 

 degree the competitor, of the great Newton, many of whose 

 discoveries he claimed for himself. He was undoubtedly 

 one of the greatest inventors that ever existed. We owe to 

 him the first investigation of and discovery of the isochronal 

 properties of springs, and their application to regulate the 

 motions of a watch. This escapement is a very good one. 

 It is one of the simplest in construction; at the same time, 

 it requires the most delicate adjustment and first-class 

 workmanship. The impulse is given directly, so that it goes 

 without oil ; but it never allows the balance to be perfectly 

 free from the train, as the long tooth is always rubbing 

 against the axis. It requires less frequent cleaning than the 

 lever, and, with careful wearers, gives equally good results. 

 Where, however, it is subjected to a rotatory motion, such as 

 many people give to their watches in the action of winding 

 them, it is liable to set — that is, to stop — owing to the 

 motion communicated to it. It also occasionally trips — that 

 is, allows two teeth to pass the notch instead of one — when 

 the motion is such as to accelerate the balance. This 

 escapement, owing to its inferiority to the lever for general 

 use, was gradually dying out. It has, however, been lately 

 made in large numbers of very cheap watches by the 

 Waterbury Watch Company, in America. 



The horizontal, as it was called, to distinguish it from the 

 old vertical escapement, and now usually known as the 

 cylinder escapement, was invented by the celebrated 

 English watchmaker, Graham, about the year 1720. It was 

 never largely used in the country of its birth, but it was so 

 extensively adopted by the French and Swiss that at one 



