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

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1differs in ſpecies from a right motion? If it be violent, how is it
that a fiery dart flying upwards, ſparkling over our heads at a
ſtance from the Earth, but not turning about, &c.
Of the mixt
tion we ſee not the
part that is
lar, becauſe we
partake thereof.
SALV. It hath been ſaid already very often, that the circular
motion is natural to the whole, and to its parts, whilſt they are in
perfect diſpoſure, and the right is to reduce to order the parts
diſordered; though indeed it is better to ſay, that neither the
parts ordered or diſordered ever move with a right motion, but
with one mixed, which might as well be averred meerly circular:
but to us but one part onely of this motion is viſible and
vable, that is, the part of the right, the other part of the circular
being imperceptible to us, becauſe we partake thereof.
And this
anſwers to the rays which move upwards, and round about, but we
cannot diſtinguiſh their circular motion, for that, with that we our
ſelves move alſo.
But I believe that this Author never thought
of this mixture; for you may ſee that he reſolutely ſaith, that the
rays go directly upwards, and not at all in gyration.
SIMP. Quare centrum ſphære delapſæ ſub Æquatore ſpiram
ſcribit in ejus plano: ſub aliis parallelis ſpiram deſcribit in cono?
ſub Polo deſcendit in axe lineam gyralem, decurrens in ſuperficie
cylindricâ conſignatam? (In Engliſh to this purpoſe:) Why doth
the centre of a falling Globe under the Æquinoctial deſcribe a
ſpiral line in the plane of the Æquator; and in other parallels
a ſpiral about a Cone; and under the Pole deſcend in the
axis deſcribing a gyral line, running in a Cylindrical
cies?
SALV. Becauſe of the lines drawn from the Centre to the
cumference of the ſphere, which are thoſe by which graves
fcend, that which terminates in the Æquinoctial deſigneth a
cle, and thoſe that terminate in other parallels deſcribe conical
ſuperficies; now the axis deſcribeth nothing at all, but continueth
in its own being.
And if I may give you my judgment freely, I
will ſay, that I cannot draw from all theſe Queries, any ſenſe that
interfereth with the motion of the Earth; for if I demand of this
Author, (granting him that the Earth doth not move) what would
follow in all theſe particulars, ſuppoſing that it do move, as
pernicus will have it; I am very confident, that he would ſay that
all theſe effects would happen, that he hath objected, as
niences to diſprove its mobility: ſo that in this mans opinion
ceſſary conſequences are accounted abſurdities: but I beſeech
you, if there be any more, diſpatch them, and free us ſpeedily