75 0 hutton’s Calculations to afcertain 
time that would have been required in the other way. 
This method I have inveftigated partly from fome hints 
of the honourable henry cavendish, f. r. s. and partly 
from fome of my own, which had been communicated 
to the Aftronomer Royal in the years 1774 and 1775 : 
of which method and its invefiigation I fliall now give 
fome account. 
Of all the methods of dividing the plan into a great 
number of fmall parts, I have found that to be the mod 
convenient for the computation, in which it is firft di- 
vided into a number of rings by concentric circles, and 
thefe again divided into a fufficient number of parts by 
radii drawn from the common center, that center being 
the obfervatory where the plummet is placed on which 
the effect of attraflion is to be computed. By this means 
the plan is divided into a great number of fmall quadri- 
lateral fpaces, two of the oppofite fides of which are 
fmall portions of adjacent circles, and the other two are 
the intercepted fmall parts of two adjacent radii, as ap- 
pears by fig. i. tab. x. in which, for the prefent, 
let the circles and their radii be fuppofed to be drawn at 
any diftances whatever from each other, till it fliall ap- 
pear from the theorem to be inveftigated what may be the 
propereft diftances and pofitions of thofe lines. In this 
figure a is the obfervatory, an the meridian, nae an 
a Eaft- 
