( T»° ) 
the Clock to go flower, by lengthening its Pendulum, 
Mr. Graham took Notice of the lowed Point, to which 
the Spirits funk at London in the Winter, 1731 and 
the greateft Height to which they rofe in the foilow- 
ingSuminer; and comparing the Motion of the Spi* 
rits in this Thermometer, with the Alterations in ano- 
ther made with Qjaickfilver, which he has for fome 
Years madeufeof; he concluded, that at London 
the Spirits in this Thermometer would ftand ( ’comma - 
nibus Annis) about 60 Divifions higher in Summer 
than in Winter. 
By feveral Years Experience, he has likewife found, 
that his Clocks (of the fame fort with Mr. Camp- 
bell’s) when expofed, as ufual, to the different De- 
grees of Heat and Cold of our Climate, do not vary 
in their Motion above 27 or 30 Seconds in a Day. 
From thefe Obfervations and Experiments there- 
fore we may reafonably conclude, that fuflicient Al- 
lowance will be made for the Lengthening of the Pen- 
dulum by Heat, if we fuppofe the Clock, upon that 
Accounr, to go one Second in a Day flower, when 
the Spirits of this Thermometer ftand two Divifions 
higher, and in the fame Proportion for other Heights. 
Admitting then, that the mean Height of the 
Thermometer, while the Clock was compared with 
the Stars at Jamaica , exceeded that at London be- 
tween 15 and 20 Divifions? if we allow 8, or 9 
Seconds, upon that Account, the remaining Differ- 
ence- muff be wholly owing to the Difference of the 
Force of Gravity in the two Places. 
Upon comparing the Obfervations, it appears, that 
in one apparent Revolution of the Stars, the Clock 
went 2' 6"; flower in Jamaica , than at London ; de- 
ducing 
r 
