LECT. IV.] ON PERSPECTIVE* 125
our recreation, and our ftudy. Happy the Genius,
whofe enlightened fkill attains to an agreeable imi-
tation of them ! Happy the Artift, whofe works,
inftead of tedious fimilarity, prefent thofe finking,
and energetic, compofitions, which arevifible alone
to the ingenious, and to the well-informed !
This may be a proper place to enquire by what
principle fome objects, or fome parts of an object
appear to advance, and others to retire. It is, be-
caufe the light from that part of a furface neareft:
to the eye, has fo much greater force than that from
the further end of the fame furface: this effect, al-
though dependent on the principles of perfpe£tive,
is yet very much changed by the obliquity of a
furface, by the fituation of a luminary, or by the
nature of an object; all which caufes vary the de-
gree, and the force of reflection.
In looking at this mahogany table, the hither part
of its furface, that adjoining the edge neareft to us9
feems enlightened ; this light at a very fmall diftance
indeed, becomes moderated; a little further off, it
is yet more decreafed, and, as we advance toward
the other extremity, it ceafes to be light, and may
lather be denominated a flight fhade. This effect
as very gradual, regular, and ccnftanr, becaufe
the furface is uniform; and, confequently, its obli-
quity or declination from the eye is uniform alfo:
but, if in any part of the table we place a furface
fomevvhat more elevated in its pofition (as this draw-
ing-board) the neareft edge of that furface does not
perfectly correfpond in its degree of light with that
vol. in. Edit. 7. p. part
our recreation, and our ftudy. Happy the Genius,
whofe enlightened fkill attains to an agreeable imi-
tation of them ! Happy the Artift, whofe works,
inftead of tedious fimilarity, prefent thofe finking,
and energetic, compofitions, which arevifible alone
to the ingenious, and to the well-informed !
This may be a proper place to enquire by what
principle fome objects, or fome parts of an object
appear to advance, and others to retire. It is, be-
caufe the light from that part of a furface neareft:
to the eye, has fo much greater force than that from
the further end of the fame furface: this effect, al-
though dependent on the principles of perfpe£tive,
is yet very much changed by the obliquity of a
furface, by the fituation of a luminary, or by the
nature of an object; all which caufes vary the de-
gree, and the force of reflection.
In looking at this mahogany table, the hither part
of its furface, that adjoining the edge neareft to us9
feems enlightened ; this light at a very fmall diftance
indeed, becomes moderated; a little further off, it
is yet more decreafed, and, as we advance toward
the other extremity, it ceafes to be light, and may
lather be denominated a flight fhade. This effect
as very gradual, regular, and ccnftanr, becaufe
the furface is uniform; and, confequently, its obli-
quity or declination from the eye is uniform alfo:
but, if in any part of the table we place a furface
fomevvhat more elevated in its pofition (as this draw-
ing-board) the neareft edge of that furface does not
perfectly correfpond in its degree of light with that
vol. in. Edit. 7. p. part