DOI Page / Citation link:
https://doi.org/10.11588/diglit.18826#0173
LECT. ON PERSPECTIVE. 121
v Very far North," fays Captain James, who win-
tered up Hudfon's Bay, " we found the fun to rife
twenty minutes before it mould, and in the evening,
to remain about twenty minutes longer than it
mould"—and this refraction (horiens the polar
winter a whole month; as well as proJongs ever/
day the cheerful fight of the fun in thofe parts.
The refractive power of the air, has alfo a re-
markable effect on the form of the fun, and the
moon, when near the horizon, changing them, from
the circular form of which we know they mould be,
to an oval form, and, efpecially, raifing (and there^
by flattening) the under limb, fo much, that the ge-
neral form of the object is of no true mathematical
figure : this I mvfelf have obferved in a confiderable
degree: though I fuppofe no degree which ever
occurs in this country, can equal what often occurs
in the north.
But not to one region only is the principle of
aerial refraction confined, for, in the warmer climates
of the eaft it has its influence. Dr. Shaw, fpeak-
ing of Arabia round about Mount Sinai, inform*
us, that when thefe defarts are fandy, and level,
the horizon is as fit for aftronomical obfervations as
at fea, which at a diftance thefe parts nearly re-
femble. It was there furprifing, to obferve in what
an extraordinary manner every object appeared to
be magnified; for a fhrub feemed as big as a tree,
and a flock of Achbobbas (birds the fize of a Capon)
might be miftaken for a caravan of camels. " This,"
3 fays
v Very far North," fays Captain James, who win-
tered up Hudfon's Bay, " we found the fun to rife
twenty minutes before it mould, and in the evening,
to remain about twenty minutes longer than it
mould"—and this refraction (horiens the polar
winter a whole month; as well as proJongs ever/
day the cheerful fight of the fun in thofe parts.
The refractive power of the air, has alfo a re-
markable effect on the form of the fun, and the
moon, when near the horizon, changing them, from
the circular form of which we know they mould be,
to an oval form, and, efpecially, raifing (and there^
by flattening) the under limb, fo much, that the ge-
neral form of the object is of no true mathematical
figure : this I mvfelf have obferved in a confiderable
degree: though I fuppofe no degree which ever
occurs in this country, can equal what often occurs
in the north.
But not to one region only is the principle of
aerial refraction confined, for, in the warmer climates
of the eaft it has its influence. Dr. Shaw, fpeak-
ing of Arabia round about Mount Sinai, inform*
us, that when thefe defarts are fandy, and level,
the horizon is as fit for aftronomical obfervations as
at fea, which at a diftance thefe parts nearly re-
femble. It was there furprifing, to obferve in what
an extraordinary manner every object appeared to
be magnified; for a fhrub feemed as big as a tree,
and a flock of Achbobbas (birds the fize of a Capon)
might be miftaken for a caravan of camels. " This,"
3 fays