1poſite blank, if the ſight were made in one onely point; but if we
ſhould find, that the edges of the white cartel appear diſcovered,
it ſhall be a neceſſary argument that the viſual rayes do not iſſue
from one ſole point. And to make the white label to be hid by
the black, it will be requiſite to draw neerer with the eye:
Therefore, having approached ſo neer, that the intermediate
bel covereth the other, and noted how much the required
proximation was, the quantity of that approach ſhall be the
tain meaſure, how much the true concourſe of the viſive rayes, is
remote from the eye in the ſaid operation, and we ſhall moreover
have the diameter of the pupil, or of that circlet from whence
the viſive rayes proceed: for it ſhall be to the breadth of the
black paper, as is the diſtance from the concourſe of the lines,
that are produced by the edges of the papers to the place where
the eye ſtandeth, when it firſt ſeeth the remote paper to be hid
by the intermediate one, as that diſtance is, I ſay, to the diſtance
that is between thoſe two papers. And therefore when we
would, with exactneſſe, meaſure the apparent diameter of a Star,
having made the obſervation in manner, as aforeſaid, it would be
neceſſary to compare the diameter of the rope to the diameter of
the pupil; and having found v.g. the diameter of the rope to be
quadruple to that of the pupil, and the diſtance of the eye from
the rope to be, for example, thirty yards, we would ſay, that the
true concourſe of the lines produced from the ends or
ties of the diameter of the ſtar, by the extremities of the
meter of the rope, doth fall out to be fourty yards remote from
the ſaid rope, for ſo we ſhall have obſerved, as we ought, the
portion between the diſtance of the rope from the concourſe of
the ſaid lines, and the diſtance from the ſaid concourſe to the
place of the eye, which ought to be the ſame that is between
the diameter of the rope, and diameter of the pupil.
ſhould find, that the edges of the white cartel appear diſcovered,
it ſhall be a neceſſary argument that the viſual rayes do not iſſue
from one ſole point. And to make the white label to be hid by
the black, it will be requiſite to draw neerer with the eye:
Therefore, having approached ſo neer, that the intermediate
bel covereth the other, and noted how much the required
proximation was, the quantity of that approach ſhall be the
tain meaſure, how much the true concourſe of the viſive rayes, is
remote from the eye in the ſaid operation, and we ſhall moreover
have the diameter of the pupil, or of that circlet from whence
the viſive rayes proceed: for it ſhall be to the breadth of the
black paper, as is the diſtance from the concourſe of the lines,
that are produced by the edges of the papers to the place where
the eye ſtandeth, when it firſt ſeeth the remote paper to be hid
by the intermediate one, as that diſtance is, I ſay, to the diſtance
that is between thoſe two papers. And therefore when we
would, with exactneſſe, meaſure the apparent diameter of a Star,
having made the obſervation in manner, as aforeſaid, it would be
neceſſary to compare the diameter of the rope to the diameter of
the pupil; and having found v.g. the diameter of the rope to be
quadruple to that of the pupil, and the diſtance of the eye from
the rope to be, for example, thirty yards, we would ſay, that the
true concourſe of the lines produced from the ends or
ties of the diameter of the ſtar, by the extremities of the
meter of the rope, doth fall out to be fourty yards remote from
the ſaid rope, for ſo we ſhall have obſerved, as we ought, the
portion between the diſtance of the rope from the concourſe of
the ſaid lines, and the diſtance from the ſaid concourſe to the
place of the eye, which ought to be the ſame that is between
the diameter of the rope, and diameter of the pupil.
* Striſce.
How to find the
diſtance of the rays
concourſe from the
pupil.
How to find the
diſtance of the rays
concourſe from the
pupil.
SAGR. I have perfectly underſtood the whole buſineſſe, and
therefore let us hear what Simplicius hath to alledge in defence of
the Anti-Copernicans.
therefore let us hear what Simplicius hath to alledge in defence of
the Anti-Copernicans.
SIMP. Albeit that grand and altogether incredible
nience inſiſted upon by theſe adverſaries of Copernicus be much
moderated and abated by the diſcourſe of Salviatus, yet do I
not think it weakened ſo, as that it hath not ſtrength enough left
to foil this ſame opinion. For, if I have rightly apprehended the
chief and ultimate concluſion, in caſe, the ſtars of the ſixth
nitude were ſuppoſed to be as big as the Sun, (which yet I can
hardly think) yet it would ſtill be true, that the grand Orb [or
Ecliptick] would occaſion a mutation and variation in the ſtarry
Sphere, like to that which the ſemidiameter of the Earth
ceth in the Sun, which yet is obſervable; ſo that neither that, no
nience inſiſted upon by theſe adverſaries of Copernicus be much
moderated and abated by the diſcourſe of Salviatus, yet do I
not think it weakened ſo, as that it hath not ſtrength enough left
to foil this ſame opinion. For, if I have rightly apprehended the
chief and ultimate concluſion, in caſe, the ſtars of the ſixth
nitude were ſuppoſed to be as big as the Sun, (which yet I can
hardly think) yet it would ſtill be true, that the grand Orb [or
Ecliptick] would occaſion a mutation and variation in the ſtarry
Sphere, like to that which the ſemidiameter of the Earth
ceth in the Sun, which yet is obſervable; ſo that neither that, no
zoom in
zoom out
zoom area
full page
page width
set mark
remove mark
get reference
digilib