•with a Dead Beat Scape ment and Deal Pendulum. 35 



marks on the subject, hoping at the same time that they may 

 be the means of calling the attention of your readers to this 

 curious circumstance, and which appears to be general in a 

 greater or less degree, under certain atmospheric variations ; 

 and is moreover too important to be overlooked, in every case 

 where great accuracy is required. 



These variations in the supplementary arc of vibration, are 

 in many cases of much greater consequence to the accurate 

 going of a clock, than theory would seem to point out ; and 

 what is worse, perhaps no two clocks can be found, that, un- 

 der the same circumstances of angular vibration, would have 

 their rates affected in an equal degree ; as the thickness and 

 length of the suspension spring, the nature and accuracy of 

 the scapement, the weight of the pendulum, and the power 

 applied to keep the clock in motion, — all have, a tendency, 

 more or less, to affect the result 



With a given power, weight of pendulum, and dead beat 

 scapement, might not a suspension spring be made of such a 

 length and thickness as perfectly to neutralize the eflfect on 

 the rate, which would arise from an increase or decrease in 

 the arc of vibration ? 



Although I have in the paper above alluded to given some 

 account of the clock on which these observations were made, 

 yet perhaps it may not be amiss to say something more in 

 this place respecting it. 



This clock has a very perfect dead beat scapement, and the 

 train is of the very best workmanship ; the balance-wheel is 

 of brass, and the pallets of steel : there is no jewelling in any 

 part. The pendulum weighs twelve pounds, and is so deli- 

 cately hung, that a very small maintaining power at the pal- 

 lets is sufficient to keep it in motion ; there are two tangent 

 screws for adjusting the beat, and a graduated nut and index 

 for regulating the rate. 



Now from the observations which I have made on the vi- 

 brations of the pendulum of this clock, I have found that they 

 are at times regular, or nearly so, for several days together ; 

 and on the other hand, they are frequently very irregular, va- 

 rying several times in the day, and that too, without any ap- 

 parent cause ; but in general 1 have observed the arcs most 

 variable, when much cirri, cirrostrati, and highly electrified 

 cumuli appear in the atmosphere, and also on the approach of 

 stormy weather ; yet this is not always the case, for sometimes 

 the pendulum has a very unsteady motion even in fine and 

 serene weather. I have also found that the same anomaly 

 takes place in clocks with recoiling scapemcnts, and probably 

 in others of the most highly finished workmanship, a circum- 



V'2 



