Defcription of an improved 21eBrometer. zyi 



forks are. (liewn by the feclions of the two brafs caps FF, as 

 are alfo the two knife edges LL. By thefe caps the efcapc 

 of the elcftric matter is partly prevented, 



A brafs ring Q, capable of being moved along the ftiort 

 arm of the upper beam AB, fliews, by means of marks de- 

 termined by trial and cut out on the beam, the number of 

 grains wliich muft he placed in the fmall fcale to reftore the 

 equilibrium of the beam at each diftance of the ring Q from 

 the point of fufpenfion. 



On the long arm CD of the lower beam there is alfo a 

 moveable ring S, which, like the ring Q, fliews in grains, 

 by its diftance from the point of fufpenfion, the power re- 

 quifite to overcome the preponderance of LD in regard to 

 LC. 



The power neceflfary for this purpofe will be found if the 

 fliell H, which weighs exadly fourteen grains, be fuffered to 

 fmk down on the glafs plate C, and the ring S be puflied . 

 forwards till both the arms of the beam are in equilibrium. 

 The part of the beam on which the ring S has moved is <li- 

 vided into fourteen parts, fo that o marks the place where 

 the rinc S mull; (land when the beam, in its free Hate, Is 

 in equilibrium; and 14 ftands at the place where the ring 

 S ajrain reftores a perfect equilibrium when the {hell H is 

 laid on the glafs plate C. Each of thcfc parts, which arc 

 divided into quarters, indicates a grain. The lower divifion* 

 of the fcale will be found with more accuracy if quarters of 

 a grain be put, in fuccefiion, into the fliell H (after it has 

 been laid on the plate C), and the ring S be moved betweea 

 each quarter of a grain until the perfcft equilibrium be re- 

 (lored. This place on the beam is then to be marked, and 

 you may continue in this manner until the 30th part of a 

 grain be given. Both fcales, for the fake of diftinftnefs, are 

 divided only fo low as quarters of a grain ; though the inftru- 

 ment is fo delicate, and muft abfolutely b& fo, that i-20th of 

 a grain is fufficient to deftrov the equilibrium. 



The two glafs pillars M and N, together with the fteel 



forks 



