INFLUENCE OF SUSPENSION ON WATCH. 379 



detached lever watch. The amount of the effect 

 will of course be much less for a marine chrono- 

 meter, not removed from its gimbals, but suspended 

 by cords attached to its outer case, on account of 

 the great addition of moment of inertia due to the 

 outer case. With a marine chronometer, or any 

 watch having a chronometer escapement (Harri- 

 son's), or having a duplex escapement, the seconds 

 hand jumps forward once, and one comparatively 

 loud beat is heard, for each period of the balance- 

 wheel ; and thus it is easy to see whether the watch, 

 when suspended, is vibrating according to the first 

 fundamental mode (losing), or the second mode 

 (gaining), by noticing in which direction the visible 

 motion is at each beat of the escapement. With 

 either of these kinds of escapement the experi- 

 ments above described arc liable to stop the watch 

 when the upper points of support are adjusted for 

 the critical arrangement. Thus, for instance, if the 

 points of support have first been too close for the 

 critical arrangement, and are gradually separated 

 until the vibration of the frame becomes very 

 large, a great gain of rate is produced ; and if the 



