28 IMPROVEMENT of TIME-PIECES. 



pendulum towards the perpendicular will be as much ac- 

 celerated. Thefe two forces therefo ■ will deftroy each 

 other, and the pendulum will perform its vibrations in 

 equal times, whether the air be light or heavy, denfe or 

 rare. 



1 have for greater perfpicuity defcribed the moft limple 

 cafe, but perhaps not the moft eligible, for if we can en- 

 large the velTel or body C, in any proportion, the dif- 

 tance of its center from A may be diminilhed at the fame 

 rate. 



However plaufible the above may appear in theory, 

 no doubt difficulties will occur when we attempt to re- 

 duce it into practice. But I am perfuaded they will not 

 be found infuperable. 



The only experiment I have hitherto made on this 

 fubjed: has been merely to fhew that a pendulum can be 

 made in this manner which iTiall vibrate quicker in a 

 denfe medium than in one more rare, contrary to what 

 takes place with common pendulums. 



I made a compound pendulum on the principles above 

 mentioned, of about one foot in its whole length. This 

 pendulum, on many trials, made in the air 57 vibrations 

 in a minute. On immerfing the whole in water it made 

 59 vibrations in the fame time, fhewing evidently that 

 its motion was quicker in fo denfe a medium as water 

 than in the air. When the lower bob or pendulum only 

 was plunged in water it made no more than 44 vibrations 

 in a minute. The remaining i 5, being folely the effedt 

 of the preiTure of the water againft the upper veffel G. 



On 



