( M 2 ) 
IV. Experiments relating to the ^efiflance of Fluids , 
made before the Royal Society on Thurfday, 
March the 5 ol/;, 1 7 1\ . tfo ^e^erend J. T. 
Defaguliers, LL. D. F. % S . 
I Took a Ball of Gold of an Inch in Diameter, that 
had a little Stem of the fame Metal, with a place 
on it to fallen a String to - 9 and having fufpended 
it by a lilken Thread too ftrong to lengthen by 
ftretching, 1 made the Diltance between the Center 
of the Ball, and the Point of Sufpenlion equal to 12,5 
Inches, then caufing the Ball to vibrate in a Trough 
full of Water, (which had an upright Piece of Wood 
in the middle of one fide with Pins or Keys from 
which the Ball hung, that the Center of Sufpenlion 
might always be in the fame place) I obferv’d by 
looking from a Pin on one fide of the Trough to a 
mark made oppofite to it on the other fide, whereabouts 
the String of the Pendulum ("juft above the Surface 
of the Water j in which the Ball was quite immers’d) 
went after 14 Vibrations- and by another Pin and 
oppofite mark, alfo obferv’d where it went to, after 
28 Vibrations. Taking out the Water, I fill’d the 
Trough with Mercury, the length of the Pendulum , 
Point of Sufpenlion and all other things remaining 
as before : then letting go the Ball in the Mercury 
from the fame place whence it was let down when 
the Trough was full of Watery (which was mark’d 
by a String ftretched a crofs to prevent miftakes) after 
one 
