( 3M > 
From a variety of fuch Experiments, we fhould be 
enabled to determine how far Sir Ifaac Newton's 
Theory is conformable to Truth, with much greater 
certainty than from thofe Trials which are made by 
actually meafuringthe Lengths of fimple Pendulums ; 
becaufe a Difference of one hundreth Part of an Inch, 
in the Length of a Pendulum, correfponds to Eleven 
Seconds in a Day ; and it being eafv to obferve how 
much a Clock gains, or luffs in a Day^ even to a 
{Ingle Second ; it is certain, that by means of a Clock, 
compared in the manner abovementioned, we may 
diftinguifh a Difference (in the Lengths of Ifochronal 
Pendulums) of one Thoufandth Part of an Inch, or 
lefs ^ whereas it will be fcarce poffible to meafure their 
true Lengths, without being liable to a greater Error 
than that. Befides, by taking Notice how much a 
Clock gains, or lofes, upon the falling or rifing of a 
Thermometer, we can better allow for the different 
Degrees of Heat in this, than in the other Method 
of making the Experiment, by a&ualMeafurement • 
fince it may not be eafy to determine how much the 
Meafure itfelf, which we make ufe of, will be length- 
ened by different Degrees of Heat. 
For thefe Reafons, I efteern Mr. Campbell' s Expe- 
riment to be the moft accurate of all that have hi- 
therto been made, and propereft to determine the Dif- 
ference of the Gravity of Bodies in different Latitudes 
and therefore I (hall fubjoin a Table, which I com- 
puted from it, containing the Difference of the Lengtli 
of a fimple pendulum, Twinging Seconds at the /Equa- 
tor, and at every fifth Degree of Latitude, together 
with the Number of Seconds that a Clock .would 
gain in a Day,, in thofe feveral Latitudes.,, fuppofing> 
. it 
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