Pjg NEW COMPENSATION PENDULUM, 



expanded ments, which gave precisely the same result, the expansion 

 •0049 inch pej of 4 feet of white deal was determined to be 0*0205 parts of 

 of heat. ^" ^^^^ ^^^^ ^*^^° ^^ Fahrenheit's thermometer, fronj 



which by proportion we get 0*0049 parts of an inch for the 

 expansion of one foot with 180° difl'erence of temperature^ 

 1 shall now attempt to give a general description of the 

 pendulum, and then proceed to a more particular account of 

 the manner in which it is constructed. 

 Pendulum de- A B C D, PL V, fig. 1, is oast in zinc. From A to B 

 is one inch ; and from C to D nearly two inches : The height 

 of A C is ten inches. Above A B a piece of brass is sol- 

 dered, an inch square and half an inch thick, through which 

 a hole is made four tenths of an inch in diameter, and tap- 

 ped with a very fine screw. A cylinder of zinc, E F, about 

 two inches and a half in length, has a screw on it to fit that 

 in the piece of brass as accurately as possible. This cylin- 

 der should be carefully turned in a lathe, on a hole as a cen- 

 tre about the eighth of an inch diameter, and made quite 

 through it; the top of the cylinder to the length of a quar- 

 ter of an inch is filed square, for the purpose of more readily 

 turning the screw with a key, or pincers : and there is a thin 

 plate of brass, represented at c, d, which screws on the cy- 

 linder, in order to fix it firmly at any height. 



In the bottom plate of zinc, C D, a hole is made half an 

 inch in diameter, through which the pendulum spring pas- 

 ses, and the whole is fastened by four screws to the cock of 

 the time-piece, which is represented by fig 2, and which is 

 cast for the purpose with the addition of a plate of brass on 

 which the compensation rests. 

 / A steel wire, g, h, with a fine screw on it, passes through 



the hole in the cylinder of zinc, by means of which, and 

 the nut below g, the pendulum is shortened or lengthened. 

 The watch spring, which supports the pendulum, is fastened 

 to the steel wire at A, by means of a pin, and, passing 

 through a slit in the plate of brass on which the compensa- 

 tion . ests, is attached to the end of the pendulum rod in the 

 manner hereafter described. 



The rod of the pendulum is made of white deal, three 

 quarters of an inch broad, and four tenths of an inch thick, 

 and is chosen perfectly free from knots, and welkseasoned. 



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