8. Fifthly, And to shew that the Beams that fall on Black Bodies, as they
do not Rebound Outwards to the Eye, so they are Reflected towards the Body
it self, as the Nature of those Erected Particles to which we have imputed
Blackness, requires, we will add an Experiment that will also confirm our
Doctrine touching Whiteness; Namely, that we took a Broad and Large Tile,
and having Whitened over one half of the Superficies of it, and Black'd the
other, we expos'd it to the Summer Sun; And having let it lye there a
convenient time (for the Difference is more Apparent, if it have not lain
there too long) we found, as we expected, that whilst the Whited part of
the Tile remained Cool enough, the Black'd part of the same Tile was grown
not only Sensible, but very Hot, (sometimes to a strong Degree.) And to
satisfie some of our Friends the more, we have sometimes left upon the
Surface of the Tile, besides the White and Black parts thereof, a part that
Retain'd the native Red of the Tile it self, and Exposing them to the Sun,
we observ'd this Last mention'd to have Contracted a Heat in comparison of
the White, but a Heat Inferiour to that of the Black, of which the Reason
seems to be, that the Superficial Particles of Black Bodies, being, as we
said, more Erected, than those of White or Red ones, the Corpuscles of
Light falling on their sides, being for the most part Reflected Inwards
from one Particle to another, and thereby engag'd as it were and kept from
Rebounding Upwards, they communicate their brisk Motion, wherewith they
were impell'd against the Black Body, (upon whose account had they fallen
upon a White Body, they would have been Reflected Outwards) to the Small
parts of the Black Body, and thereby Produce in those Small parts such an
Agitation, as (when we feel it) we are wont to call Heat.
Pages:
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145