is Royal Society of London. 
_ To prevent any difturbance from currents that might’be 
produced within the box that contained the balance, by even 
the difference of temperature that might be occafionedl by 
~ 
heat being communicated by the bait of the experimenters 
to one fide of it more than another, it was fupported in the 
- iniddle of a clofe room ; the operators, from adjoining apart- 
ments, viewed the operation through holes in the wall by 
means of telefcopes ; and the apparatus had a ftrong light 
thrown upon its two ends (an opening being left at each end 
of the box for the purpofe) by means of two lamps, alfo in 
the adjoining apartments, the rays from which were like- 
w rife made to pafs through holes formed in the wall. 
The two large balls were fufpended from a beam near the 
cieling, which could be moved in an horizontal direétion, 
‘by means of a firing and pulley, fo as to be brought near to 
the. {mall balls of the balance, or made to recede again with- 
out requiring any perfon to be in the room, 
From this defeription it will be eafily feen that, on the 
two large balls being brought near to the two {mall ones, but 
“on ‘oppofite fides of each ‘that their forces may not counteract 
each other, the fall fufpending wire of the balance mutt be 
twvilted by the movements of the arms, occafioned. by at- 
traction, Which carries the fmall towards the large balls ; 
and that the wire endeavouring to, untwift itfelf will again 
‘in ‘its turn ‘carry the fmall balls away from the’ Jarge ones. 
‘Vibrations aré thus occafioned, which would continue a Jong 
time before the fmall balls would fettle between the: firft 
“point ‘of réft and the large balls: but it is notmeceflary to 
wait for” this; an ivory-feale at each end ‘of the: balance 
is enables the experimenters, by means of their telefcopes, 
to fee the two “extreme divifions to'which the fmall balls 
“move in their vibrations, and thus’ to determine the) mid- 
“die point, ° The time neceffary for each erationetgaailp 
noticed. : TEL y he 
It would be impoffible in a fhort. notice to ai ‘alka to 
Mr. 
