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two Seconds in an Hour flower, when the Vibrati- 
ons were largeft, and lefs and lefs, as the Air was 
re-admitted, and the Vibrations Ihortened. 
But notwithftanding the Times were flower, as 
the Vibrations were larger, yet I had Reafon to 
conclude, that the Pendulum really moved quicker 
in Vacuo , than in the Air , becaufe the fame Differ- 
ence, or Enlargement of the Vibrations (as two 
Tenths of an Inch on a Side) would caufe the 
Movement, inftead of two Seconds in an Hour, 
to go 6 or 7 Seconds flower in the fame time \ as I 
found by nice Experiments. 
The next Experiments I fhall mention, I made 
at feveral Times, in 1705, 1706, and 1712, by 
the Help of a good Month-Piece that fwings Se- | 
conds. The Weight that then drove it, was about 
12 or 13 Pounds, and it kept Time exadtly by the 
Sun’s mean Motion : But by hanging on 6 Pounds 
more, the Vibrations were enlarged 5 but yet the 
Clock gained 13 or 14 Seconds in a Day. 
And as the Increafe or Diminution of the Power 
that drives the Clock, doth accelerate or retard 
its Motion, fo, no doubt, doth Cleannefs or 
Foulnefs affed it, and fo doth Heat and Cold 5 for all 
have the fame Effed: upon the Pallets and Pendulum. 
The laft Experiments I fhali mention, I made in 
3716 and 1718, to try what Effects Heat and 
Cold had upon Iron Rods of the fame Length, or 
as near as i could to thofe that fwing Seconds. 
I made my Experiments with round Rods of< about 
a Quarter of an Inch Diameter, and with fquare 
Rods, of about three Quarters of an Inch Square. j : 
The Effects on both which were the fame. 
At 
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