S48 Notice regarding a Time-Keeper in the Hall 



Here, it will be obvious, there can be no friction between 

 the teeth and the pallets, and that oil would be superfluous. 

 The rubbing has been transferred from the surfaces of the pal- 

 lets to their centres, where, from the slowness of the motion and 

 the smallness of the space moved through, there can be no appre- 

 tiable resistance between the pivots and their ruby holes, and 

 therefore no oil can be required. 



It will be observed, on inspection of the drawing, that the 

 diameter of the pallets is nearly as great as the distance between 

 the teeth of the wheel ; the teeth, however, advance only half of 

 that space at each vibration, and if the pallets were solid cylin- 

 ders, the returning motion of the pendulum would be opposed 

 by their striking against the teeth on the entering side. In or- 

 der to prevent this, a portion of the cylinder is cut away in the 

 middle part, leaving only enough of surface for the teeth to act 

 on during their descent of half the diameter. A third part of the 

 circumference is sufficient for this action, and any thing less than 

 a half will leave a free passage for the disengaged tooth. In 

 Fig. 2, at d e, the pallets are drawn as detached from their frames, 

 and as if half of the circumference were cut away from the mid- 

 dle part. In Fig. 3. and 4. the pallets are shewn in section in 

 their proper positions : in these figures, w is a small counter- 

 poise, to bring back the pallet to its position for receiving the 

 next succeeding tooth, after it has been turned aside by the es- 

 caping one. 



To persons who have paid attention to the subject of Horo- 

 logy, I need not point out the great value of this improvement, 

 nor the benefits which may arise from it in those departments of 

 science where an exact measure of time is a desideratum*. 



* The maintaining power in this clock is a weight of 41b. 4oz., descending 

 through about 40 inches in 7 days ; the weight of the pendulum and ball 12J lb., 

 and of vibration 4.4 inches. 



