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I. An Inquiry concerning the Figure of Inch 
Planets as revolve about an fuppofmg 
the Denjity continually to vary, from the 
Centre towards the Surface $ by Mr. Alexis 
Clairaut, F. R. S. and Member of the Royal 
Academy of Sciences at Paris. Tranjlated 
from the French by the Rev . John Colfon 
Lucas , prof Math . Cantab, and F. R . S. 
N Otwithftanding that Part of Sir Ifaac New- 
tons Mathematical Principles of Natural 
Philofophy , where he treats of the Figure of 
the Earth, is deliver'd with the ufual Skill and Ac- 
curacy of that great Author; yet I thought fomething 
farther might be done in this Matter, and that new 
Inquiries may be propofed, which are of no fmall 
Importance, and which poffibly he overlook'd, 
through the Abundance of thofe fine Difcoveries he 
was in Purfuit of. 
What at firft feem'd to me worth examining, when 
I apply'd myfelf to this Sub j eft, was to know why 
Sir* Ifaac affumed the Conical Ellipfis for the Figure 
of the Earth, when he was to determine its Axis? 
For he does not acquaint us why he did it, neither 
can we perceive how he had fatisfied himfelf in this 
Particular: And unlefs we know this, I think we 
cannot intirely acquiefce in his Determinations of the 
Axes of the Planets. It feems as if he might have 
took any other oval Curve, as well as the conical 
Ellipfis of Apollonius , and then he would have come 
to other Conclufions about thofe Axes. 
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