Richmond dispatch. [volume] (Richmond, Va.) 1884-1903, 1888-09-23

small proportion OF those who read these
lines have ever noticed the sky surface
looking fat / have observed the APP
pearance myself three or four times
during my life, but then l have always
been on the lookout for it, this particu-
lar illusion having long had great inte-
rest for me. The occasions when the
Gatness OF the under surface OF
the cloud sky can be recognized
are those when the clouds lie
actually in long parallel beds OF
tolerably uniform breadth and separated
from each other by tolerably equal dis
tanccs and lying at the same general
level-the sun being near the horizon, so
as TO illuminate the cloud-bands under
meath. At such times, as also when IN
stead of uniform bands, kind OF net
work OF clouds covers the sky toward the
place of the horizon sun, an effect OF
foreshortening is produced which brings
ont the horizontally of the cloud sur
fnce-that is. not of the surface of indi-
yidual clouds, but of the general layer
A BEAUTIFUL ILLUSION.
/ remember one occasion when / was
travelling across the western pralrles, to-
ward the time of sunset, that as the sun
in bis descending motion passed from
above 10 below a LAYER of clouds uni
formly reticulated, the golden tinge along
an edge Of each Of the cloud streaks so
distinctly indicated the relative positions
of the different parts OF the network OF
clouds, that the true fiatness of the sur
face was as strongly forced on me as usu-
ally the incorrect arcbed form is I'M
pressed on the mind. For the first and
only time in my life | was not only able
(as on three or four other occasions) but
actually forced to feel what an immense
globe this earth world of ours is. For
there was the widely spanning surface OF
cloud looking perfectly flat though really
part of the inner surface Of an immense
spherical shell.
There is a converse illusion familiar
only to balloonists, which Is to be ex-
planned in the same way. Rising high
above the earihs surface III balloon,
we sec the surface of the earth beneath
arched into the fOrmof an immense bowl
or basin. The mind refuses to admit
/ the thought that the exceedingly
minute depression OF the visible
horizon corresponds to the seem
inglv immense depth Immediately
below the aeronaut. Or one may
say Though in reality it is saying the
same thlnR) that the mind cannot admit
the thought OF the immensely of the dis
lance of the horizon. From height of
/ half a mile the horizon Is some forty
miles away or eighty times further than
the earth's surface below, but the mind
sets the horizon only three or four miles
away cat least if the air is clear and con-
seouently the surface which regarded
| as a whole is really slightly convex be-
| low the observer appears to be markedly
| concave.
Draw a series of concentric circles
having radii uniformly increasing, so
| that the circumference are equally dis
/ tant Athwart these, about midway be-
/ tween the common centre and the outer
most circumference, draw straight line.
/ This line will appear curved. If series
OF equi-distant waved lines are drawn
and straight line is drawn athwart
them parallel to the direction OF the
waves, it will appear wavy.
Hundreds of kindred illusions could
DO cited did space permit. a whole
volume might in fact be written respect
ing illusions affecting shape and size
alone. But we have others to consider.
Among illusions affecting color some
OF the most important and interesting
are those which painters have to take
into account in producing with paque
tints. the effects Of sunlight or moon
light, the CLEAN of metals and kindred
illusions. All snch effects are necessa-
rilv illusory, deity though they may be
producedl
ARTISTIC BFFECTS-
A painter who should strive to repre-
sent q sun-ilumined lily by simply using
the strongest white tints at his command
would fail utterly. By using dark tints
he obtains the effect of brightness,
where by using bright tints he only OBJ
tains dirtv-looking white. So with me-
talic effects which are often admirably
caught in paintings | may cite a
striking example in Landseers painting
"War," where the culras of the slam
troopers CLEANSE as if actually metallic. 1t
is related of the French painter Delaroche
that be had tried again and again to pro-
duce fair imitation Of cleaning gold in
one of his historical paintings. Giving
ND the attempt in despair be sent for a
fiacre TO take him to the gallery of Lux
embOurg, where were some paintings IN
which the desired effect had been OBJ
tanned, that he might learn the secret.
But 10 rs he came down the door-steps
the yellow wheels Of the tiacre glowed
in tho sunlight with the very effect he
wanted they looked like wheels OF gold
for the nonce, though colored only with
the coarse yellow used by coach painters
Whence the illusion Delaroche caught
the idea iii a moment, dismissed the
farce, and returned TO isstudio to work
out successfully the effect which for days
he had been vainly striving to attain.
The yellow OF the farce wheels was
picked out with bright purple, by con-
trast with which the bright but coarse
yellow seemed to shine with a golden
CLEAN. This was the whole secret which
Delaroche would have learned from the
paintings Of the old masters.
As regards distance, every picture
drama in true perspective shows how
false effects of distance may bepreserved.
But We find in nature illusions which con-
stantly deceive us in this respect Haze
and mist make objects appear far of
which are really near; clouds on the ho'
rizon appear near though really far of.
Wherever an objects apparent size is
mistaken its distance is misiudged. and
vSce UcrSd. But probably false effects OF
distance are more frequently produced
10y differences in the clearness of the me-
dun through which objects are seen
than in any other way. Every one who
has travelled in regions where the air is
exceptionally clear can recall illusions oil
this sort. At Denver thought the
snow-clad hills / saw when looking down
certain street were Just beyond the
streets end they we're really not hills al
all, but mountains many miles distant.
SO at Fort Laramie, it seemed to me that
ii would pleasantly occupy my mornings
leisure to stroll over to certain snowy
knobs which | could not have reached
with less than days travelling.
R,~u4prN DDccrop