308 New Pendulum Escapement 



In almost all delicate escapements, high finish in the rubbing 

 surfaces and great accuracy in the workmanship are absolutely 

 essential to good going. In every case the advantage of careful 

 execution cannot fail to be felt; but in this escapement that ad- 

 vantage is by no means great. The execution of the train is al- 

 most a matter of indifference ; and even in the most vital part, 

 though the distances of the detaining teeth were inaccurately 

 laid off, the errors would recur at every revolution of the escape- 

 ment wheel, and their effects on the going would be generated 

 and destroyed in the same period, so that the daily or hourly 

 rate could not be affected. 



The motion of the train resembles that of a perfect dead-beat, 

 although the escapement certainly partakes of the nature of the 

 recoil, since the unhooking of the spring is only effected after a 

 slight elevation of the impeller. The beat is made only at each 

 second oscillation, so that, in order to beat seconds, a half seconds 

 pendulum must be used. In escapements which beat at each 

 vibration, it is difficult to have two consecutive intervals exactly 

 equal, — the one being less, and the other as much more than an 

 exact second ; but when the beat is given only on one side, no 

 such inequality can exist. 



The parts of the impeller are liable to expansion by heat, but 

 the effects of this can easily be obviated by extending an arm 

 made of some expansive metal such as zinc, on the other side of 

 the axis B, while the branches represented in the figure are 

 made of glass. This arm also will allow a weight to be slid 

 along it so as to regulate the intensity of the impulse. 



When the spring is released from the pin F, it does not merely 

 assume its position of rest, but continues for a moment to vibrate 

 on each side of it. As there might appear to be some risk of its 

 catching again the same pin, a damper has been put on to di- 

 minish these oscillations ; but, as in some other escapements which 

 I have constructed on the same principle, it was not found ne- 

 cessary, it has been omitted in the drawing. 



I need hardly point out to the Society, that the number of 

 lifting pins is not limited to four, and will leave the considera- 

 tion of the simplicity of the machinery, and its fitness for pro- 

 ducing the desired end, to themselves. 



