[ S4i ] 
was hung by the fide of the clock, and he never faw 
it higher than 744- divifions, nor lower than 67, 
from the 12th of 1761 to the 18th of January 1762. 
He has given no defcription of the clock. 
Remark. 
The method propofed by Mr. Mafon, of making 
thefe obfervations , by means of the occultations 
of bars behind the ridge of rocks, was certainly 
better than the other, by means of the equal altitude 
inftrument j for it has been found by experience, that 
any inftrument, however fecurely fixed, is liable to 
alterations in its diredion, owing, perhaps, to the 
effeds of heat and cold, moifture and drynefs, in the 
parts, to which the inftrument is fattened* and an 
equal altitude inftrument was the moft improper for this 
purpofe, becaufe it could not be redified by looking 
at a diftant mark, to corred any alterations it might 
have buffered in its pofttion or diredion. 
Mr. Mafon further fays, that, by comparing the 
obfervations of the going of the clock, made at St. 
Helena, with thofe made at the cape of Good Hope, 
the difference of the effed of gravity at the two places 
may be found. 
Remark. 
No obfervations of the difference in the going of a 
clock, made at different places, can, with certainty, 
determine the difference of the effed of gravity at 
thefe places 5 becaufe it has been found, by expe- 
rience, that the fame clock, placed at different times 
on different walls, in the fame room, will ^ make a 
