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. I have been
lately inform'd, that an Observation near of Kin to Ours, has been made by
some Learned Men in _France_ and _Italy_, by long Exposing to a very Hot
Sun, two pieces of Marble, the one White, the other Black; But though the
Observation be worthy of them, and may confirm the same Truth with Our
Experiment, yet besides that our Tryal needs not the Summer, nor any Great
Heat to succeed, It seems to have this Advantage above the other, that
whereas Bodies more Solid, and of a Closer Texture, though they use to be
more Slowly Heated, are wont to receive a Greater Degree of Heat from the
Sun or Fire, than (_Caeteris paribus_) Bodies of a Slightest Texture; I have
found by the Information of Stone-cutters, and by other ways of Enquiry,
that Black Marble is much Solider and Harder than White, so that possibly
the Difference betwixt the Degrees of Heat they receive from the Sunbeams
will by many be ascrib'd to the Difference of their Texture, rather than to
that of their Colour, though I think our Experiment will make it Probable
enough that the greater part of that Difference may well be ascrib'd to
that Disposition of Parts, which makes the one Reflect the Sunbeams Inward;
and the other Outwards. And with this Doctrine accords very well, that
Rooms hung with Black, are not only Darker than else they would be, but are
wont to be Warmer too; Insomuch that I have known a great Lady, whose
Constitution was somewhat Tender, complain that she was wont to catch Cold,
when she went out into the Air, after having made any long Visits to
Persons, whose Rooms were hung with Black. And this is not the only Lady I
have heard complain of the Warmth of such Rooms, which though perhaps it
may be partly imputed to the _Effluvia_ of those Materials wherewith the
hangings were Dy'd, yet probably the Warmth of such Rooms depends chiefly
upon the same Cause that the Darkness does; As (not to repeat what I
formerly Noted touching my Gloves,) to satisfie some Curious Persons of
that