C 519 3 
manner of applying a column of it to the pendulum 
of a clock, in order to prevent the inequalities arifing 
from its different lengths by the effects of heat and 
cold ; which fucceeded accordingly, and is what is 
now called Mr. Graham’s quickfilver-pendulum. 
Mr. Graham, in the fame paper, takes notice, 
that, tho’ the pendulum of a clock was to remain 
invariable, yet there would ftill be fome irregularities 
in the motion of the clock, arifing from the fricftion 
of the different parts of the clockwork, and from the 
different degrees of foulnefs. 
In the year 1725”, Mr. John Harrifon, of Barrow 
in Lincolnfhire, made feveral experiments upon wires 
of different metals, in order to find their different 
degrees of expanfion and contraction : For he thought, 
that, by a proper combination of wires of two dif- 
ferent metals, differing confiderably in their expan- 
fion and contraction, he might be enabled to keep 
the centre of ofcillation of a pendulum always at the 
fame diftance from the point of fufpenfion. In con- 
fequence of thefe experiments, he made a pendulum, 
confiding of one fteel wire, at the end of which is 
the bob or weight, and, on each fide of this wire, 
four wires alternately brafs and fteel, fo difpofed and 
contrived, as to raife the pendulum the fame quantity 
as it is lengthen’d by heat, and to let down the pen- 
dulum in the fame proportion as it is raifed by cold. 
He made alfo a drawing of a clock, in which the 
wheels are difpofed in a different manner from thofe 
then in ufe ; which drawing I have feen, figned by 
himfelf in the year 1725-. Two of thefe clocks with 
pendulums, as defcribed above, were finifhed in the 
year 1726. In thefe clocks Mr. Harrifon has made 
a particular 
