1white, but not burniſhed; would this yet ſuffice to the making
of it viſible, and apt for darting forth the light of the Sun?
of it viſible, and apt for darting forth the light of the Sun?
SALV. It would ſuffice in part; but would not give a light ſo
ſtrong, as it doth being mountainous, and in ſum, full of
eminencies and great cavities. But theſe Philoſophers will never
yield it to be leſſe polite than a glaſſe; but far more, if more it
can be imagined; for they eſteeming that to perfect bodies perfect
figures are moſt ſutable; it is neceſſary, that the ſphericity of thoſe
Cœleſtial Globes be moſt exact; beſides, that if they ſhould
grant me ſome inequality, though never ſo ſmall, I would not
ſcruple to take any other greater; for that ſuch perfection
ing in indiviſibles, an hair doth as much detract from its perfection
as a mountain.
ſtrong, as it doth being mountainous, and in ſum, full of
eminencies and great cavities. But theſe Philoſophers will never
yield it to be leſſe polite than a glaſſe; but far more, if more it
can be imagined; for they eſteeming that to perfect bodies perfect
figures are moſt ſutable; it is neceſſary, that the ſphericity of thoſe
Cœleſtial Globes be moſt exact; beſides, that if they ſhould
grant me ſome inequality, though never ſo ſmall, I would not
ſcruple to take any other greater; for that ſuch perfection
ing in indiviſibles, an hair doth as much detract from its perfection
as a mountain.
SAGR. Here I meet with two difficulties, one is to know the
reaſon why the greater inequality of ſuperficies maketh the
ger reflection of light; the other is, why theſe Peripatetick
tlemen are for this exact figure.
reaſon why the greater inequality of ſuperficies maketh the
ger reflection of light; the other is, why theſe Peripatetick
tlemen are for this exact figure.
SALV. I will anſwer to the firſt; and leave to Simplieius the
care of making reply to the ſecond. You muſt know therefore,
that the ſame ſuperficies happen to be by the ſame light more or leſs
illuminated, according as the rayes of illumination fall upon them
more or leſſe obliquely; ſo that the greateſt illumination is where
the rayes are perpendicular. And ſee, how I will prove it to your
ſenſe. I bend this paper, ſo, that one part of it makes an angle
upon the other: and expoſing both theſe parts to the reflection of
the light of that oppoſite Wall, you ſee how this ſide which
ceiveth the rayes obliquely, is leſſe ſhining than this other, where
the reflection fals at right angles; and obſerve, that as I by
degrees receive the illumination more obliquely, it groweth
weaker.
care of making reply to the ſecond. You muſt know therefore,
that the ſame ſuperficies happen to be by the ſame light more or leſs
illuminated, according as the rayes of illumination fall upon them
more or leſſe obliquely; ſo that the greateſt illumination is where
the rayes are perpendicular. And ſee, how I will prove it to your
ſenſe. I bend this paper, ſo, that one part of it makes an angle
upon the other: and expoſing both theſe parts to the reflection of
the light of that oppoſite Wall, you ſee how this ſide which
ceiveth the rayes obliquely, is leſſe ſhining than this other, where
the reflection fals at right angles; and obſerve, that as I by
degrees receive the illumination more obliquely, it groweth
weaker.
The more rough
ſuperficies make
greater reflection
of light, than the
leſs rough.
ſuperficies make
greater reflection
of light, than the
leſs rough.
Perpendicular
rays illuminate
more than the
lique, and why.
rays illuminate
more than the
lique, and why.
SAGR. I ſee the effect, but comprehend not the cauſe.
SALV. If you thought upon it but a minute of an hour, you
would find it; but that I may not waſte the time, ſee a kind of
demonſtration thereof in Fig. 7.
would find it; but that I may not waſte the time, ſee a kind of
demonſtration thereof in Fig. 7.
SAGR. The bare ſight of this Figure hath fully ſatisfied me,
therefore proceed.
therefore proceed.
SIMPL. Pray you let me hear you out, for I am not of ſo
quick an apprehenſion.
quick an apprehenſion.
SALV. Fancie to your ſelf, that all the paralel lines, which you
ſee to depart from the terms A. B. are the rays which fall upon the
line C. D. at right angles: then incline the ſaid C. D. till it hang
as D. O. now do not you ſee that a great part of thoſe rays which
peirce C. D. paſs by without touching D. O? If therefore D. O.
be illuminated by fewer rays, it is very reaſonable, that the light
received by it be more weak. Let us return now to the Moon,
ſee to depart from the terms A. B. are the rays which fall upon the
line C. D. at right angles: then incline the ſaid C. D. till it hang
as D. O. now do not you ſee that a great part of thoſe rays which
peirce C. D. paſs by without touching D. O? If therefore D. O.
be illuminated by fewer rays, it is very reaſonable, that the light
received by it be more weak. Let us return now to the Moon,