APPENDIX. 



" The whole is contained in a ftrong brafs frame, 

 " fcrewed on the top of a three-legged wooden ftand, 

 " three feet four inches high : the front legs extend three 

 " feet eight inches in the diredlion of the vibration, and 

 *' the back leg extends three feet four inches from each of 

 " the front legs, at which diftance the three legs are 

 ** fo conneded at bottom, by horizontal rods, that 

 *' they cannot poffibly alter their relative portion ; by 

 ** thefe means the point of fufpenfion of the pendulum 

 *' is rendered much more immovable than could be 

 " done in any portable clock having a cafe of the ufual 

 *' dimenfions, without great trouble, and an apparatus ill 

 " fuited for experiments of this nature. 



" In the middle of the horizontal bar that connects the 

 " front legs is fixed a piece of filvered-glafs, by means of 

 *' which the whole machine is readily adjufted to its 

 ** proper pofition : the lower part of the pendulum- 

 " ball hangs diredly over this mirror, on which is drawn 

 " a line from back to front ; and when the Image of a 

 fmall pin, which is fcrewed into the lower part of the 

 pendulum, is feen bifefted by this line viewed direftly in 

 " front, the pofition of the machine is properly adjufted. 



" On the back leg of the ftand, Immediately behind the 

 ** pendulum, is a hook to hang a thermometer on, for 

 *' making frequent obfervations of the temperature of ths 

 " air. In order to prepare for an experiment, the pendulum 



A a . "is 



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