DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.18826#0122
LECT. iii.] on perspective. 85
But, though w light is pleafant, and it be a
cheerful thing to behold the fun," yet is too much
of this invaluable bleffing not only ufelefs, but inju-
rious : fo that, befide the wonderful provifion made
in our vifual organs for excluding redundance, our
fenfe of fight is alfo not a iittie refrelhed by revi ving
fhade; efpecially if for a length of time it has
been expofed to the action of intenfe light.,
If Shadow be merely an interruption of luminous
rays, we may, without reluctance, bellow a few
minutes attention on fome of the properties of
light, fince perhaps by enquiring into thefe, we
may more eafily comprehend their contraries. The
rapidity of light is fo vehement, that it is juftly
considered as to us inftantaneous, fo that direclly as
a body is expofed to it, or removed from it, the
effect is vifible; but, thofe laws whereby the
courfe of light, or of luminous rays, is determined,
more nearly concern the fubject of our attention.
For, if, inftead of conftantly keeping a direct line,
its courfe" was oblique, or fpiral, or volutory in any
manner, we mould be to feek for different principles
whereby to afcertain, and to explain, its progrefs:
but, as by the Almighty Jiat, which faid " LtGht
be, and light was," it takes invariably the neareft
courfe from point to point, we acquire, by a fimple
experiment, a perfect knowledge of the principles
which determine its direction.
Whoever will interpofe an opaque body be-
tween the origin, and fource, of light, natural, or
artificial, and any proper fubftance expofed to its
rays, will eafily perceive their illuminations are pre-
vol. in. Edit. 7. m eluded
But, though w light is pleafant, and it be a
cheerful thing to behold the fun," yet is too much
of this invaluable bleffing not only ufelefs, but inju-
rious : fo that, befide the wonderful provifion made
in our vifual organs for excluding redundance, our
fenfe of fight is alfo not a iittie refrelhed by revi ving
fhade; efpecially if for a length of time it has
been expofed to the action of intenfe light.,
If Shadow be merely an interruption of luminous
rays, we may, without reluctance, bellow a few
minutes attention on fome of the properties of
light, fince perhaps by enquiring into thefe, we
may more eafily comprehend their contraries. The
rapidity of light is fo vehement, that it is juftly
considered as to us inftantaneous, fo that direclly as
a body is expofed to it, or removed from it, the
effect is vifible; but, thofe laws whereby the
courfe of light, or of luminous rays, is determined,
more nearly concern the fubject of our attention.
For, if, inftead of conftantly keeping a direct line,
its courfe" was oblique, or fpiral, or volutory in any
manner, we mould be to feek for different principles
whereby to afcertain, and to explain, its progrefs:
but, as by the Almighty Jiat, which faid " LtGht
be, and light was," it takes invariably the neareft
courfe from point to point, we acquire, by a fimple
experiment, a perfect knowledge of the principles
which determine its direction.
Whoever will interpofe an opaque body be-
tween the origin, and fource, of light, natural, or
artificial, and any proper fubftance expofed to its
rays, will eafily perceive their illuminations are pre-
vol. in. Edit. 7. m eluded