Salusbury, Thomas, Mathematical collections and translations (Tome I), 1667

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1the ſame part, and not by it divided. Therefore the Center of Gravity
of the ſaid Conoid is not below the point N: Neither is it above.
For,
if it may, let it be H: and again, as before, ſet the Line L O by it ſelf
equalto the ſaid H N, and divided at pleaſure in S: and the ſame pro­
portion that B N and S O both together have to S L, let the Conoid
have to R: and about the Conoid let a Figure be circumſcribed conſi­
ſting of Cylinders, as hath been ſaid: by which let it be exceeded a leſs
quantity than that of the Solid R: and let the Line betwixt the Center
of Gravity of the circumſcribed Figure and the point N be leſſer than
S O: the remainder V H ſhall be greater than S L.
And becauſe that as
both B N and O S is to SL, ſo is the
169[Figure 169]
Conoid to R: (and R is greater
than the exceſs by which the circum­
ſcribed Figure exceeds the Conoid:)
Therefore B N and S O hath leſs pro­
portion to S L than the Conoid to the
ſaid exceſs.
And B V is leſſer than
both B N and S O; and V H is grea­
ter than S L: much greater proporti­
on, therefore, hath the Conoid to the
ſaid proportions, than B V hath to
V H.
Therefore whatever proporti­
on the Conoid hath to the ſaid pro­
portions, the ſame ſhall a Line greater
than B V have to V H.
Let the ſame be M V: And becauſe the Center
of Gravity of the circumſcribed Figure is V, and the Center of the
Conoid is H. and ſince that as the Conoid to the reſt of the proportions,
ſois M V to V H, M ſhall be the Center of Gravity of the remaining
proportions: which likewiſe is impoſſible: Therefore the Center of
Gravity of the Conoid is not above the point N: But it hath been de­
monſtrated that neither is it beneath: It remains, therefore, that it ne­
ceſſarily be in the point N it ſelf.
And the ſame might be demonſtrated
of Conoidal Plane cut upon an Axis not erect.
The ſame in other terms,
as appears by what followeth:
PROPOSITION.
The Center of Gravity of the Parabolick Co­
noid falleth betwixt the Center of the cir­
cumſcribed Figure and the Center of the in­
ſcribed.

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