t08 , On the Rate of a Clock unlh a fVooden renduhnn. [Jan. 



VI. — Dn the Rale of a Clock ivif.h a Wooden Penduhi.w ; and on ike 

 loi)giiudi?ial Expansion and Coiilraction of Wood. — J^i/ Lieutenant 

 Braddock. 



1. — Being in the practice of amusing myself during leisure hours in 

 experimental and philosophical pursuits, I took a fancy, about a year 

 ago, to make up an astronomical clock, intending it to be a correct time- 

 keeper, if T could but command sufficient dexterity and skill in the 

 mechanical department to make the parts of the clock work smoothly, 

 and to finish them in an efficient manner. Having an engine for cut- 

 ting the teeth of wheels, w'hich I constructed some years ago, a small 

 turning lathe, and other necessary tools and implements, I commenced 

 operations, and being a tolerable amateur workman found no difficulty 

 in finishing an 8-day clock, wath Graham's dead-beat escapement and a 

 pendulum vibrating seconds. 



2. ~A compensating pendulum being a tedious thing to make, and to 

 adjust to mean time, I made enquiries and read all I could find about 

 pendulums with wooden rods, and ascertaining that a piece of clean 

 grained dry fir, or deal, made a very capital substitute for the more 

 complex metallic compensating pendulum, I adopted it for my clock ; 

 and have the pleasure to send you its rate of going, with a few re- 

 marks, and some experiments on the longitudinal contraction and ex- 

 pansion of wood. 



3. — I was somewhat perplexed at the outset by contradictory opi- 

 nions regarding the propriety of varnishing, or not varnishing, the 

 pendulum rod ; some writers considering it necessary, and others not. 

 I adopted however the opinion of the former, thinking that the wood 

 would be less pervious to humidity, and consequently be less affected 

 by changes of the atmosphere, if it was well coated with varnish; but 

 at the same time I fitted up an apparatus, hereafter described, with a 

 micrometer, in order to ascertain whether well seasoned wood did 

 change its length from hygrometric causes. I have reason to conclude, 

 from the experiments I have made, that it does, and that to too consi- 

 derable an extent in this part of India, to prevent its successful use 

 for the particular purpose now under notice. 



4. — In order to remove doubt with reference to those who may take 

 an interest in such enquiries as the present, it is necessary to state that 

 the wood, employed for the pendulum rod, was clean grained American 



