Mr AIRY ON A NEW CONSTRUCTION OF THE GOING-FUSEE. 221 



will immediately depress d till the end of/"is firmly lodged upon a tooth 

 of the ratchet : and then, inasmuch as the toothed-wheel is carried by the 

 lever-frame at its center b and is thrust by the click f connected with the 

 lever-frame, the continued descent of d will carry the toothed-wheel in just 

 the same manner as if it were part of the lever-frame ; and therefore the 

 toothed-wheel will for the time revolve about a. 



The two conditions therefore, which are required in the change of forces 

 acting on the lever ab c are entirely satisfied ; and therefore the pressure at 

 c during the winding up of the clock will be the same as during the ordi- 

 nary going of the clock. 



The following description of the movement may perhaps facilitate the 

 understanding of the action of this mechanism. 



While the clock is going in its ordinary way, the weight W descends, 

 turning the barrel and wheel in such a direction that the teeth of the inter- 

 nal ratchet glide under the click f without producing on it or sustaining 

 from it any effect. The action of the weight W and the resistance of the 

 pinion at c produce a certain pressure on the lever-frame at b which causes 

 the end d to assume a determinate position, in which it remains without 

 motion so long as the weight W acts. 



As soon as the pressure of W is relieved, the pressure on b ceases ; the 

 weight w preponderates, the end d drops, the end of f is thrust firmly 

 against a tooth of the ratchet, and the continued action of w causes the 

 toothed wheel to turn in a piece with the lever-frame round the center a, 

 and thereby to produce a pressure at c, which, if a correspond exactly to 

 the place at which W acted on the barrel, is exactly equal to the pressure 

 which formerly actd at c. 



If the action of W be suspended for a long time, the continued descent 

 of d will bring d nearer to the vertical passing through a, and will thereby 

 diminish the statical moment of w, and consequently will diminish the 

 pressure at c. In this regard the action of this mechanism is exactly similar 

 to that of the going-spring in Harrison's going-fusee. 



