176 Col. Beuufoy on the Going of a Clock [Mauch, 



continued heat and dryness of the summer season, and the 

 early commencement of winter, which to the present time has 

 continued with excessive severity. 



Neio Matton, Jan. 4, 1820. JaMES StoCKTON. 



Article IV. 



On the Going of a Clock with a Wooden Pendulmn. 

 By Col. Beaufoy, F.R.S. 



(To Dr. Thomson.) 



MY DEAR SIR, , Bushey Heath, Feb. 1 ; IH^O. 



To determine what reliance could be placed on the going of a 

 clock with a wooden pendulum, I fitted one of my monthly regu- 

 lators, beating dead seconds, and whose motion continued while 

 winding up, with a straight-grained cyhndrical deal rod ; but 

 being dissatisfied with the irregularity of the rate, I was on the 

 point of rejecting this, when, from the circumstance of the clock 

 Ijecoming much out of beat, I concluded the great source of 

 error might probably proceed from the waiping of the wood. I, 

 therefore, caused the intermediate portion of the deal, about an 

 inch below that part where the watch spring which suspends the 

 pendulum is fastened to the upper part of the bob, to be reduced 

 from a cylindrical to an eliptical shape, the transverse, or longest 

 diameter being parallel to the back of the clock ; this alteration 

 so much improved the going, that I am induced to trouble you 

 with a table containing the rate for 12 months, and to remark 

 that the rod was perforated in the centre for the crutch to pass 

 through, and a brass eye inserted to prevent the wearing away 

 of the wood. To render the pendulum steady, it was hung 

 independent of the frame that supports the clock ; and the bob, 

 in lieu of being screwed to the rod, was permitted to rest upon a 

 divided nut, turning on a fine screw, attached to the lower extre- 

 mity of the rod, and which answered the twofold purpose of 

 supporting this weight, and regulating the pendulum. The 

 advantage of permitting the bob to remain unconfined to the 

 rod is, that the expansion of the bob upwards has a tendency to 

 counteract the expansion of that spring by which the pendulum 

 is hung downwards, and of, therefore, preserving the same length. 

 By examining the table, it will be found that the accuracy of the 

 simple pendulum described is little inferior to the compound one, 

 known by the name of the gridiron pendulum ; and when it is 

 also considered that the latter costs 12 guineas, and the rod not 

 as many pence, the variation of the going bears so small a pro- 

 portion to the difference of price, that it will, generally speaking, 

 be sufficiently accurate for most purposes. I remain, 



Mi' dear Sir, yours, very sincerely, Mark Beaufoy. 



