[ 812 ] 
variation however will fcarce be obfervable, but as it' 
is real, it may not be thought amifs to determine 
what its precife quantity is. 
I am fenfible the following theory, as far as it re- 
lates to the motion of Jupiter’s fatellites, is imperfect 
and might be profecuted further ; but being hindered 
at prefent from fuch purfuit by want of health and 
other occupations, I thought I might fend it you in 
the condition it has lain by me for fome time. You 
can beft judge how far it may be of ufe, and what 
advantage might arife from further improvements in 
it. I am glad to have this opportunity of giving a 
frefh teftimony of that regard which is due to your 
diftinguifhed merit, and of profeffing myfelf with the 
highefl efteem, 
Reverend Sir, 
Bath, 0 £b 21. 
1758. 
Your very humble Servant, 
C. Walmefley. 
Lemma I. 
Invenire gravitatcm corporis longinqai ad circumfe- 
rentiam circuli cx particulis materice in duplicate! 
ratione diftantiarum inverse attrahentibus conjian- 
tem. 
P Sto NIK (Fid. Tab. xxxiii. Fig. 1.) circumferen- 
' tia circuli, in c.ujus pun&a omnia gravitct corpus 
longinquum S locatum extra planum circuli. In hoc 
planum agatur linea perpendicularis SII, et per cir- 
culi centrum X ducatur redla HXK lccans circuluin 
in I ct K, et SR parallela ad HX : producatur au- 
\cm. S H ad dilfantiam datam SD, et agantur redta? 
