( 4 ’ ) 
gree of Expanfion, that I obferved in it,' when placed’ 
near the Fire, beyond what I had conceived to be in 
fo denfe a Fluid, immediately fuggefted to me the Ufe 
that might be made of it, by applying it to a Pendu- 
lum. In a few Days after, I made the Experiment, 
but with much too long a Column of Quickhlver, the 
Clock going flower with an increafe of Cold, contrary 
to the common Pendulum ; however, it was a greater 
Confirmation of the Advantage to be expeded from it, 
fince it was eafy to fhorten the Column in any Degree 
required. The only Doubt I entertained was, left 
there Ihoujd not be a proportional Expanfion and Con- 
tradion between the Quicklilver, and the Rod of the 
Pendulum, through the various Degrees of Pleat and 
Cold, frjrn the one Extreme to the other. To make 
this Experiment the more convincing, I placed the 
Clock in a Part of the Houfe, the moft expofed of any 
to the Changes of Heat and Cold, the Room having no 
Fire in it in the Winter, and expofed to a South Sun, 
with Leads above it, which, in the Summer, made it 
extremely hot. I hung a Thermometer by it, and had 
like wife another Clock at no greater Diftance from it, 
than was neceflary to keep the Cafes from touching 
one another. This Clock had been made fome Years 
before, with extraordinary Care, having a Pendulum 
about 6o Pounds in Weight, and not vibrating above 
one Degree and half from the Perpendicular and 
which, in a more temperate Situation, had not alter’d 
above 12 or 14/' in 24 Hours, between Winter and 
Summer ^ but in this Place it altered 30^^ a Day, be- 
tween the hotteft and coldeft Weather, in the Year 
1722, a Year no way remarkable for either Extremes. 
But this great Alteration was owing to the Situation I 
mentioned above, and which I made Choice of for the 
fake of making the Experiment the more fenlible. 
F The 
