[ ,544 ] 
with the Sun’s limb to the north and fouth alter- 
nately, half the difference of the two meafures, re- 
duced to a given time by allowing for the motion of 
the planet by calculation, will be the difference of 
declination of the centers of the Sun and planet at 
that time, without any regard to the diameters of the 
Sun or planet, or the error of adjuffment of the 
micrometer. And this would be a better oblervation 
than meafuring the difference of declination of the 
limbs of the Sun and planet by bringing them both 
in contact with the fume wire parallel to the equa- 
tor defcribtd above ; as the meafuring diftances from 
the Sun’s eafl or well: limb in lines parallel to the 
equator is a better obfervation than meafuring dif- 
ferences of right afcenfion of the limbs by time. 
By thefe two obfervations of diffances of an inferior 
planet from the Sun’s limb in lines parallel and per- 
pendicular to the equator, its true place with refpedl 
to the Sun’s center may be accurately afeertained 
during any part of its tranfit over the Sun’s difk; 
and confequently its nearefl approach to the Sun’s • 
center and the time of the ecliptic conjundlion may 
be deduced vvith great exadtnefs, although the middle' 
of the tranfit diould not be feen, and the Sun flaould 
be vifible only for a fmall fpace of time fufiicient 
for taking thefe obfervations. 
The following order of making the feveral obfer- 
vations with Dollond’s micrometer in the late tranfit 
of YTmis was recommended to the obfervers who 
went on the part of the Royal Society to the North 
Cape and to the South Sea, which may ferve to 
elucidate their obfervations. See Phil. Tranf. Vol, 
LIX. p. 266, 267. and this Vol. LXI. p.397, 418 
Inifrudtions 
