DOI Page / Citation link:
https://doi.org/10.11588/diglit.18826#0076
56 on PERSPECTIVE. [lECT.1I.
other. To demonftrate this, take any perfpective ex-
ample, turn it, till the vertical plane becomes the ho-
rizontal plane, and you will fee, evidently, that it is
governed by the fame center, and conducted by the
fame principles.
Thus far, I hope our principles are clear, and lu-
minous ; referring to the examples for certain in-
frances of their application, I fhall now offer a few
remarks relative to the introduction, and the appear-
ance, of objects reprefented in perfpeclive.
I think it moft familiar to my auditory, to revert to
the mirror, to illufirate this particular, as the reverfion
of objecls will hereafter appear to be of no real detri-
ment, or-confequence : in fact, whenever geometrical
plans of original objects are ufed (and on many occa-
lions they are to a learner very convenient), their per-
fpeclive reprefentations become reverfe; but fuch
plans are not alwavS neceffary, as, by the given di-
menfions of objecls, a matter will generally afcertain
their reprefentations.—To proceed,
That upright looking - glafs reprefents an upright
picture; the flab before it, the ground; where the
bottom of the glafs touches the flab, is, of courfe, the
ground line. I lay on the flab, this fquare board, clofe
alo*ng the bottom of the glafs, which, on looking into
the glafs, 1 fee thus: the flab, and the board are pa-
rallel to the ray fhot from the eye to the center, (or
received by the eye into its center,) which ray is per-
pendicular to the glafs. Now, as the center is the
natural vanilhing point of all lines perpendicular to
the
other. To demonftrate this, take any perfpective ex-
ample, turn it, till the vertical plane becomes the ho-
rizontal plane, and you will fee, evidently, that it is
governed by the fame center, and conducted by the
fame principles.
Thus far, I hope our principles are clear, and lu-
minous ; referring to the examples for certain in-
frances of their application, I fhall now offer a few
remarks relative to the introduction, and the appear-
ance, of objects reprefented in perfpeclive.
I think it moft familiar to my auditory, to revert to
the mirror, to illufirate this particular, as the reverfion
of objecls will hereafter appear to be of no real detri-
ment, or-confequence : in fact, whenever geometrical
plans of original objects are ufed (and on many occa-
lions they are to a learner very convenient), their per-
fpeclive reprefentations become reverfe; but fuch
plans are not alwavS neceffary, as, by the given di-
menfions of objecls, a matter will generally afcertain
their reprefentations.—To proceed,
That upright looking - glafs reprefents an upright
picture; the flab before it, the ground; where the
bottom of the glafs touches the flab, is, of courfe, the
ground line. I lay on the flab, this fquare board, clofe
alo*ng the bottom of the glafs, which, on looking into
the glafs, 1 fee thus: the flab, and the board are pa-
rallel to the ray fhot from the eye to the center, (or
received by the eye into its center,) which ray is per-
pendicular to the glafs. Now, as the center is the
natural vanilhing point of all lines perpendicular to
the