[ 355 ] 
be thereby obtained, provided they are not liable to 
any confiant and uniform caufe of error : as has 
been clearly (hewn by my late worthy and learned 
friend Mr. Thomas Simpfon, Phil. Tranf. Vol. 
XLIX. Part I. Page 82 ; and alfo in his Mifcellaneous 
Tract, Page 64. Therefore I cannot but think, 
that, from a confiderable number of fuch obftrva- 
tions, the mean horizontal parallax, and thence the 
mean equatorial parallax of the moon might be de- 
duced certainly to a tingle fecond, or ever nearer if 
required. 
In hopes of attaining fuch a degree of exadtnefs, 
I endeavoured to multiply my obfervations as much 
as poffible : yet, through the great cloudinefs of the 
ifland, could not obtain more than three nights com- 
plete obfervations. If thefe fhould appear too few to 
attain the exadtnefs propofed, yet they may contri- 
bute, in a good mealure, thereto. Plowever, 1 have 
fince had an opportunity, during my refidence at 
the ifland of Barbadoes, in the latitude of 13 0 north, 
which 3 0 degrees nearer the line than St. Helena, 
to repeat thefe obfervations to a very great number, 
from which, I doubt not, the mean equatorial par- 
allax of the moon may be accurately determined. 
I (hall here defire to remark, that, if the like ob- 
fervations were repeated in different latitudes, they 
would probably afford the bed means yet propofed 
for afcertaining the true figure of the earth ; as they 
would determine the ratio of the diameters of the 
parallels of latitude to each other, the horary par- 
allaxes being proportional thereto : and, after all 
the experiments and obfervations that have been made 
Z z 2 on 
