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XL VIII. A Propofal for meafuring the AttraBion of fome 
Hill in this Kingdom by AJironomical Obfervations. By 
the Rev. Nevil Mafkelyne, B. D. F. R. S. and AJirono- 
mer Royal, 
Redcle in the yearT p attracSlion of gravity be exerted, as 
Sir ISAAC NEWTON fuppofes, not only be- 
tween the large bodies of the univerfe, but between the ' 
minuted: particles of which thefe bodies are compofed, 
or into which the mind can imagine them to be divided, 
a6ting univerfally according to that law, by which the 
force which carries on the celeftial motions is regulated ; 
namely, that the accelerative force of each particle of 
matter towards every other particle decreafes as the 
fquares of the diftances increafe, it will necelTarily fol- 
low, that every hill muft, by its attraction, alter the di- 
rection of gravitation in heavy bodies in its neighbour- 
hood from what it would have been from the attraction 
of the earth alone, confidered as bounded by a fmooth 
and even furface. For, as the tendency of heavy bodies 
downwards perpendicular to the earth’s furface is owing 
to the combined attraction of all the parts of the earth 
upon it, fo a neighbouring mountain ought, though in a 
far lefs degree, to attraCt the heavy body towards its cen- 
tre of attraction, which cannot be placed far from the 
middle of the mountain. Hence the plumb-line of a 
quadrant, or any other altronomical inftrument, muft 
be deflected from its proper fltuation by a fmall quantity 
VoL. LXV. U u u ftars, 
