[ i6 9 ] 
to the days of conjunction, quartile, and oppofition ; 
and this as well out of the meridian as in it ; we 
can hardly doubt but that, if the weather fhould 
favour, fo many cheques would be formed, that, from 
the next oppofition of Mars alone, the affair may be 
brought within a 24th part of the whole; and, if to 
this be added the force of fuch determinations, as 
may be drawn from obfervations on Venus, before 
and after her tranfit over the Sun next year, it can 
hardly be doubted, but that thofe three will bring us 
within a fingle fecond of a degree, fubtended from 
the neareft planet ; and thefe conclufions will be fur- 
ther flrengthened by future obfervations ; as two years 
will fcarcely pafs without affording one or more oppor- 
tunities of this kind.. 
As I meant not to embarrafs myfelf with exaCt 
computations, I have conftantly fuppofed the diftance 
of the common center of gravity from the center of 
the Earth, to be a fixed quantity ; whereas it will 
vary in the fame proportion as the Moon’s diftance 
varies ; but, as this and many other minutice will pro- 
perly enter the computation, when the obfervations 
are made, I muff beg leave to refer them to the 
learned in this fcience. 
Auflhorpe, April 17, 
i;68. 
J. Smeaton. 
Vol. LVIII 
7 
XXV. 
