Richmond dispatch. [volume] (Richmond, Va.) 1884-1903, 1897-03-25
rScAxpEscENT LIGHT AND SIGHT.
No Indication That Eyesighf h"s
Been Injured by Use OF the Light

Heen En3ufF0 Dy t1f VA VIZ
GAncet
Some interesting discussion has taken
place OK late in regard TO the effect upon
the eye OF the Auer incandescent hgnt
The mantle of this incandescent system
of lighting consists, as is now pretty
generally known, OF a network OF the
rare oxides Chiefly Of thorium, with
small proportion of cerium). which, on
being heated In the Bunsen flame, emits
a brilliant, white light AS might be ex-
pected, this light Is comparatively rlch
I'm the ultraviolet or chemically acuVe
rays that are identical with those In sun
light and It has been urged that TINS
richness in actinic rays may possibly be
productive of injury to the sight. This
argument appears to be based on mea-
surements OF wave lengths, made by
means of the spectroscope. The arc
electric-light, it Is said, has similar ef-
fects, but Of a more pronounced charac-
ter. As yet there is no evidence OF ex-
perience as far as we know-and the
Welsbach light has now been in use Tor
several years-that the slightest INJURY
TO the optic mechanism where the system
has been i'm use for domestic lighting
has ever been produced; and unless a
person deliberately stared at the naked
light for some hours every day, II would
be surprising to learn that real injury
could be referred 10 this ause- II IS
well known that the radiation OF light
downward from the incandescent mantle
is feeble, so that without a reflector or
some rejecting surface at the top or
the mantle as i'm the ordinary way
would be provided by ceiling, much or
the Illuminating power would be lost.
From the particular point OF view under
discussion this is however, an advantage
for the lighting Of rooms, since rejected
and not directly-transmitted light Is
pleasanter and more agreeable TO the
eye, besides which in the phenomenon OF
reflection partial absorption takes place,
so that the light becomes pleasantly dif-
fused and of a healthy tone. In any
case. If any apprehension should exist
that the rays proceeding from an mean
descing mantle are injurious because OF
their chemical activity--an activity which
I'm sunlight gives life to the plant-world-
these days could be readily and effectuai-
ly filtered out by the simple expedient OF
surrounding the light with tinted globe
such as red or orange which need re-
duce but very little the originally high
Illuminating power. Even then the light
IS over 100 per cent. higher in illuminate
ing value than the ordinary. gas-hame'
Artificial light. of course IS most in re-
quest in the dark days Of winter and IN
that season at the best of times we receive
but little more than eight hours light
from the sun. and then frequently II Is
largely filtered from its chemically active
rays by the medium Of a murky atmos-
phere On the other hand, we enjoy IN
the summer lust twice as much sunlight,
which is then Of greatly increased power,
and the chemical activity of which Is IN
fnitely greater than could possibly be
furnished by any known form OF aru-
fetal light. Taking these simple facts
into consideration, we should almost eN-
| pect to find in some form or other some
manifestation or deterioration in the eye
| sight during the summer period, due to
largely increased exposure to the chemi-
| cally active rays OF solar light. We are
| not aware that any such manifestation
| has been observed. The argument that
! nature intended us to rest from the ef-
| fects of light as soon as the sun is below
| the horizon demands, IL il can be reason
ably applied at all, the rejection OF all
artificial means Of lighting, since there
| can be no light Of any kind OF any ana
to the eve whatever that can DE without
some chemical activity. still less prac-
| ticable does such a suggestion become
! when applied TO the lanos Of the mid
night sun and other places or to the Arc
| tic winter of several months darkness.
| Clearly this theory could only be prompted
by the consideration of the limited con-
! ditions Of environment IN the temperate
zone. No men probably are exposed more
freely and continuously TO the chemical
active rays Of the sun than our sailors,
vet their acuteness of vision and
! penetrative power Of sight Is
matter of admiration and wonder to every
one. Sunlight is by a thousand circum-
/ stances widely and uniformly dinused,
| making II more acceptable 10 the eye
| and during its journey to earth 1t under
goes an important modification, for in
passing through the air 1t IS deprived OF
| some of the red rays, while the blue
/ RAYS pass on-a circumstance which eX-
| plains the azure character or the SKY,
! In view of these facts it is difficult 70
receive the theory with any seriousness
that because there may be certain
proportion of ultra violet rays in given
artificial light, It IS necessarily injurious.
IL would be- a sorry thing II these same
rays were forever filtered out Of the
light OF the sun by the medium OF con-
slant fog or cloud, as so often happens
In the days Of winter Exposure 10
purely elementary light, as red. yellow,
or blue. does undoubtedly prove injurious,
either positively, or negatively. The dis
tress produced on working for some time
TO quote one instance In q red or yellow
light. as in the dark room Of the photo
grapher. who employs one or other or
these colors on account Of their chemi-
cal inertness, is well known. Absence
of sunlight is held 20 be synonymous with
the absence Of ME- and the life-giving
and invigorating qualities Of solar light
are largely, If not entirely, dependent
upon the chemically active rays, and
certain lines of scientific research have
shown that without the phenomenon OF
insulation going on day by day' IRE
would be unendurable and finally ex-
tineuished. White light. therefore, as
Afforded in its entirety by the sun, Is a
necessity Of existence.