'204 ' PHILOSOPHICAL TRANSACTIONS. [anNO 1675 



the barrel as soon as it has bent this spring. This piece which serves to stop, is 

 easy, and has not been thought necessary to be marked here, to avoid embarrass- 

 ing the figure. Bat while one indented part of the interrupted wheel F G, viz. 

 F, turns the barrel C, the empty parts opposed thereto, answers to the other 

 barrel M, and gives liberty to its enclosed spring to unbend itself. Thus while 

 the movement of the watch bends the small spring of the barrel C, in the same 

 time the small spring of the other barrel M unbends of itself. I say, in the same 

 time, except the spring C shall have done bending a little sooner than the spring 

 M shall have unbent itself: so that the spring C being bent, and the wheel FG 

 stopped, both of them stay in this posture, till the spring M, when it shall be 

 quite unbent, at the end of its motion, touch a piece which delivers it. And 

 then the spring C unbends of itself in its turn ; the teeth of the interrupted 

 wheel, which continues its motion the same way as before, since it is delivered, 

 not being any more able to hinder it therefrom, because the barrel C now meets 

 with the empty part H of the said wheel. But before it has done unbending 

 itself, the indented part I, being opposite to the empty part H, that turns the 

 barrel M, bends its spring again, and having done so, stops with it, while the 

 spring C, making an end of unbending itself, delivers them by a reciprocal good 

 office, and renders to the spring M the same services, which it had received 

 from it, with an expectation of receiving the like again. 



Which being well considered, it is manifest, that the same alternative motions 

 w^ill continue always : that the periods taken from the very moment that one 

 spring begins to unbend, until the moment it once unbends itself again, will 

 always be of equal duration, though the two small springs be not equally strong: 

 that the balance of such a watch will be double, and be charged more or less, 

 and receive delay, by advancing or recoiling, along the two arms, two equal 

 weights, counter-balancing one another, that so the change of the situation 

 may not at all prejudice the equality of the watch. For the rest, we may in this 

 kind of watches spare the fusee, and consequently the string or chain. It is 

 also easy to judge, that such watches as these may be of a size sufficiently 

 small ; that they will make no more noise than ordinary watches ; that they will 

 be as exact as pendulums, and cease not to go while they are winding up. And 

 though the motion of the watch -wheels maybe altered by many accidents, such as 

 are, the inequality of themotion of the great ordinary spring, I mean the first mover; 

 the more or less rubbing of the wheels according as the oil grows thinner orthicker; 

 the rust, the verdigrise, the play of the pieces, the inequality of the teeth and 

 the like; yet the periods of the small springs will not be concerned in all or any 

 of them, provided the motion of the watch-wheels have always more strength 

 than it needs to bend them again; which is in our power. And so the principle 



