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



exactly in position to the point of the barrel from which the weight W 

 depends. Suppose another weight w to be suspended from d, of such 

 magnitude that it will exactly support (acting with the fulcrum a) the 

 pressure which the lever-frame sustains at b. It will readily be remarked, 

 that if the lever-frame be bent, as shewn in the figure, no nice adjustment 

 of the weight of w is necessary. For, if the weight of w be a little too small, 

 the preponderance of the pressure at b will depress b, and will thereby throw 

 d so far in the horizontal direction that the increased power of the lever ad 

 will enable the same weight w to balance the pressure at b. In like 

 manner, if the weight w be somewhat too large, the approach of d in the 

 horizontal direction, towards the vertical passing through a, will diminish 

 its statical momentum, and thereby restore the equilibrium. The effect 

 of either of these changes on the action of the wheel-teeth is to withdraw 

 them from the teeth of the pinion by an almost infinitesimal quantity, of 

 which the effect in practice is wholly insignificant. 



We may therefore now be assured that we have provided a force acting 

 upwards at b, exactly equal and opposite to the pressure which the fulcrum 

 at b sustains during the ordinary motion of the barrel (inasmuch as our 

 force does veritably support that pressure during the ordinary motion of 

 the barrel), and competent to act with insignificant diminution of amount 

 even if b be moved. One condition therefore of the change of lever-action 

 is entirely satisfied. The other condition requires that the point a of the 

 toothed-wheel shall be made, during the process of winding up, the ful- 

 crum upon which the toothed-wheel turns for the time. But the corre- 

 sponding point a of the lever-frame is the fulcrum upon which the lever- 

 frame is able to turn for the time. Consequently all that is necessary to 

 satisfy this condition is, to contrive that, during the process of winding up, 

 the toothed-wheel shall be so connected with the lever-frame that it shall 

 have absolutely the same motion which the lever-frame has on the fulcrum 

 a; or, in other words, that the toothed-wheel and lever-frame shall (for the 

 time) move all in one piece. All that is requisite for this purpose is, to 

 make a ratchet in the inside of the ring of the toothed-wheel ; and to make 

 a click f to fall in the teeth of the ratchet, its center of motion being some 

 convenient pointy of the lever-frame. For then, upon taking off the pres- 

 sure of W and the consequent pressure downwards on b, the pressure of w 



