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

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1anſwer that ſufficeth to ſatisſie at once the courſe of the ſpots,
and the diſcourſe of the Mind.
I will explain unto you ſo much
as I remember thereof, that ſo you may judge thereon as ſeems
beſt unto you.
The Pure
patetick
phers will laugh at
the ſpots and their
Phænomena, as
illuſions of the
Chryſtals in the
Teleſcope.
Suppoſing that the apparent motions of the Solar ſpots are the
ſame with thoſe that have been above declared, and ſuppoſing the
Earth to be immoveable in the centre of the Ecliptick, in whoſe
circumference let the center of the Sun be placed; it is neceſſary
that of all the differences that are ſeen in thoſe motions, the
ſes do reſide in the motions that are in the body of the Sun:
Which in the firſt place muſt neceſſarily revolve in it ſelf (i. e.

about its own axis) carrying the ſpots along therewith; which
ſpots have been ſuppoſed, yea and proved to adhere to the
lar ſuperficies.
It muſt ſecondly be confeſt, that the Axis of the
Solar converſion is not parallel to the Axis of the Ecliptick, that
is as much as to ſay, that it is not perpendicularly erected upon
the Plane of the Ecliptick, becauſe if it were ſo, the courſes and
exitions of thoſe ſpots would ſeem to be made by right lines
rallel to the Ecliptick.
The ſaid Axis therefore is inclining, in
regard the ſaid courſes are for the moſt part made by curve lines.
It will be neceſſary in the third place to grant that the
on of this Axis is not fixed, and continually extended towards
one and the ſame point of the Univerſe, but rather that it doth
alwayes from moment to moment go changing its direction; for
if the pendency ſhould always look towards the ſelf ſame point,
the courſes of the ſpots would never change appearance; but
appearing at one time either right or curved, bending upwards
or downwards, aſcending or deſcending, they would appear
the ſame at all times.
It is therefore neceſſary to ſay, that the
ſaid Axis is convertible; and is ſometimes found to be in the
Plane of the circle that is extreme, terminate, or of the viſible
Hemiſphere, I mean at ſuch time as the courſes of the ſpots
ſeem to be made in right lines, and more than ever pendent,
which happeneth twice a year; and at other times found to be in
the Plane of the Meridian of the Obſervator, in ſuch ſort that
one of its Poles falleth in the viſible Hemiſphere of the Sun, and
the other in the occult; and both of them remote from the
treme points, or we may ſay, from the poles of another Axis of
the Sun, which is parallel to the Axis of the Ecliptick; (which
ſecond Axis muſt neceſſarily be aſſigned to the Solar Globe)
mote, I ſay, as far as the inclination of the Axis of the revolution
of the ſpots doth import; and moreover that the Pole falling in
the apparent Hemiſphere, is one while in the ſuperiour, another
while in the inferiour part thereof; for that it muſt be ſo, the
courſes themſelves do manifeſtly evince at ſuch time as they are

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