SALV. I will uſe my utmoſt endeavours to render my ſelf
intelligible, but the difficulty of the accident it ſelf, and the
great attention of mind requiſite for the comprehending of it,
conſtrains me to be obſcure. The unequalities of the additions
and ſubſtractions, that the diurnal motion maketh to or from
the annual dependeth upon the inclination of the Axis of the
urnal motion upon the plane of the Grand Orb, or, if you pleaſe,
of the Ecliptick; by means of which inclination the Equinoctial
interſecteth the ſaid Ecliptick, remaining inclined and oblique
upon the ſame according to the ſaid inclination of Axis. And the
quantity of the additions importeth as much as the whole
ter of the ſaid Equinoctial, the Earths centre being at the ſame
time in the Solſtitial points; but being out of them it importeth
leſſe and leſſe, according as the ſaid centre ſucceſſively
cheth to the points of the Equinoxes, where thoſe additions are
leſſer than in any other places. This is the whole buſineſſe, but
wrapt up in the obſcurity that you ſee.
intelligible, but the difficulty of the accident it ſelf, and the
great attention of mind requiſite for the comprehending of it,
conſtrains me to be obſcure. The unequalities of the additions
and ſubſtractions, that the diurnal motion maketh to or from
the annual dependeth upon the inclination of the Axis of the
urnal motion upon the plane of the Grand Orb, or, if you pleaſe,
of the Ecliptick; by means of which inclination the Equinoctial
interſecteth the ſaid Ecliptick, remaining inclined and oblique
upon the ſame according to the ſaid inclination of Axis. And the
quantity of the additions importeth as much as the whole
ter of the ſaid Equinoctial, the Earths centre being at the ſame
time in the Solſtitial points; but being out of them it importeth
leſſe and leſſe, according as the ſaid centre ſucceſſively
cheth to the points of the Equinoxes, where thoſe additions are
leſſer than in any other places. This is the whole buſineſſe, but
wrapt up in the obſcurity that you ſee.
The cauſes of
the inequality of
the additions and
ſubſtractions of the
diurnal converſion
from the annual
motion.
the inequality of
the additions and
ſubſtractions of the
diurnal converſion
from the annual
motion.
SALV. I have already foretold it. Nevertheleſſe we will try
whether by drawing a Diagram thereof, we can give ſome
ſmall light to the ſame; though indeed it might better be ſet
forth by ſolid bodies than by bare Schemes; yet we will help our
ſelves with Perſpective and fore-ſhortning. Let us draw
fore, as before, the circumference of the Grand Orb, [as in
Fig. 4.] in which the point A is underſtood to be one of the
Solſtitials, and the diameter A P the common Section of the
Solſtitial Colure, and of the plane of the Grand Orb or
tick; and in that ſame point A let us ſuppoſe the centre of the
Terreſtrial Globe to be placed, the Axis of which C A B,
clined upon the Plane of the Grand Orb, falleth on the plane of
the ſaid Colure that paſſeth thorow both the Axis of the
ctial, and of the Ecliptick. And for to prevent confuſion, let
us only draw the Equinoctial circle, marking it with theſe
cters D G E F, the common ſection of which, with the plane of
the grand Orb, let be the line D E, ſo that half of the ſaid
quinoctial D F E will remain inclined below the plane of the
Grand Orb, and the other half D G E elevated above. Let
now the Revolution of the ſaid Equinoctial be made, according
to the order of the points D G E F, and the motion of the
tre from A towards E. And becauſe the centre of the Earth
being in A, the Axis C B (which is erect upon the diameter of
the Equinoctial D E) falleth, as hath been ſaid, in the
tial Colure, the common Section of which and of the
Grand Orb, is the diameter P A, the ſaid line P A ſhall
whether by drawing a Diagram thereof, we can give ſome
ſmall light to the ſame; though indeed it might better be ſet
forth by ſolid bodies than by bare Schemes; yet we will help our
ſelves with Perſpective and fore-ſhortning. Let us draw
fore, as before, the circumference of the Grand Orb, [as in
Fig. 4.] in which the point A is underſtood to be one of the
Solſtitials, and the diameter A P the common Section of the
Solſtitial Colure, and of the plane of the Grand Orb or
tick; and in that ſame point A let us ſuppoſe the centre of the
Terreſtrial Globe to be placed, the Axis of which C A B,
clined upon the Plane of the Grand Orb, falleth on the plane of
the ſaid Colure that paſſeth thorow both the Axis of the
ctial, and of the Ecliptick. And for to prevent confuſion, let
us only draw the Equinoctial circle, marking it with theſe
cters D G E F, the common ſection of which, with the plane of
the grand Orb, let be the line D E, ſo that half of the ſaid
quinoctial D F E will remain inclined below the plane of the
Grand Orb, and the other half D G E elevated above. Let
now the Revolution of the ſaid Equinoctial be made, according
to the order of the points D G E F, and the motion of the
tre from A towards E. And becauſe the centre of the Earth
being in A, the Axis C B (which is erect upon the diameter of
the Equinoctial D E) falleth, as hath been ſaid, in the
tial Colure, the common Section of which and of the
Grand Orb, is the diameter P A, the ſaid line P A ſhall