C 522 3 
the fixed ftars, of the motion of the clock with this 
fort of pendulum, and from the experience of feveral 
years (during which the clock was kept conftantly 
going) he found, that the clock was liable to fudden 
flarts and jerks in its motion. Of this he informed 
Dr. Bradley, Mr. Blifs, myfelf, and feveral other 
gentlemen. This clock ftill remains in Mr. Graham’s 
houfe, in the poffeffion of his executors. 
I have been informed, that one Mr. Frotheringham, 
a quaker, of Lincolnfhire, caufed a pendulum to be 
made, confiding of two bars, one of brafs, and the 
other of fteel, fatten'd together by fcrews, with le- 
vers to raife or let down the bob ; and that thefe 
levers were placed above the bob. This clock I have 
feen, and was told by the maker, Mr. John Ber- 
ridge, that the pendulum of it was made in the year 
3738, or 1739, and that the dial-plate of it was 
engraved at Mr. Siffon’s houfe in the year 1738 : and 
this clock is in the poflettion of Mrs. Gibfon, in 
Newgate-ttreet, who has had it ever fince the year 
’ 739 - 
In the Hi ft. of the Royal Acad, of Sciences at Paris , 
for the year 1741, there is a memoire ofM. Caflini, 
in which he defcribes feveral forts of pendulums for 
clocks, compounded of bars of brafs and fteel, and 
applies a lever to raife or let down the bob of the 
pendulum, by the expanfion or contra&ion of the 
bar of brafs. He has alfo given us, in the fame 
memoire, a problem for finding the proportion, 
which the two arms of the lever Ihould have, to an- 
fwer the intended purpofe j and alfo a demonttra- 
tion of it. 
6 
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