The sun. [volume] (New York [N.Y.]) 1833-1916, 1897-03-21
1vcANDEsCENr LIGHT AND SIGHT.
No Indication That Eycsisht Has Bccn Injured
by the Use OF tho Light.

From the Lancet.
Some interesting discussion has taken place Of
late in regard to the effect upon the eye of the
Auer incandescent light. The mantle Of this In
candescent system OF lighting consists. as is now
pretty generally known, of q network OF the rare
oxides tchiefiy Of thorium with a small proper
ton OF ccriuml, which on being heated in tho
Bunsen flame emits a brilliant white light As
might be expected. this light is comparatively
rich in the ultraviolet or chemically active rays
that are identical with those In sunlight, and 1t
has been urged that this richness in actinio
rays may possibly be productive of injury
to tho sight. This argument appears to be
based on measurements OF wave lengths
made by means Of the spectroscope. Tho arc
electric light. 1t is said. has similar effects. but
OF II more pronounced character. As yet thcro
and the Weisbach light has now been in use for
several years-thet the slightest injury to the
optic mechanism where, the. system has been in
use for domestic lighting has ever been pro-
duced; and unless a person deliberately stared
at tho naked light for some hours every day It
could he REFERRED to This cause. Il is well known
that the radiation, Of light downward from the
i lnsanto &C. o men raSd Is feeble !. nt So That q, Without VT ton g
provided by q ceiling, much OF the Illuminating
however, an sdvaatage for the lighting
OF TOODb, since TeneCUeu ana not ulTeCLly
transmitted light is pleasanter and more agree
able to the eye, besides which In the phenone-
non Of refeetiSn partial absorption takes place,
prchcnsion should exist that The rays proceeding
from an incandescing mantle are injurious be-
cause OF their chemical activity-an activity
which in sunlight gives NE to The I plant w f,n a..
t taeeS o Fnyf b. o fSe siS me lfes sxpysd hea ed Of sarrogn al.
ing the light with a tinted globe, such as red or
orange which hich need nfs reduce but very little the the
the light is over, 100 per cent. higher in, ilu-
mInating value than the ordinary, gas flame.
the dafk ns DAYS 81 Of '0V Winte rs % and in r tat sem a.
son, at the best Of times, We receive
from its chemically active rays by the medium
of a murky atmosphere. On the other hand. We
light, which is then OF greatly increased power,
and the chemical activity Of which Is Infinitely
EET noWn i form 'S OF arRs GlSssiiStYy iish lpfhl TafinF 9y th aas
simple facts into consideration we should almost
expect to find In some form or other some mani
during the summer period, due to a largely
Increased eSposure 70 the chemically ae.
that any such manifestation has been
observed. Thu argument that nature In
soon seone as the sun SE is below . h horizon demands. II Il
1t can be reasonably applied at all, the rejection
Of all artificial means OF lighting, since there can
whatever that can be without some chemical ac-
tivity. Still less practicable does such a sugges-
ton become when applied to the lands OF the
Midnight sun and other places or to the arctic
winter of several, months darkness. Clearly
the consideration OF the limited conditions
OF environment in the temperate zone.
No men probably are exposed more freely
and continuously to the chemically active rays
o. the sun than our sailors, yet their acutcness
OF vision and penetrative power OF sight Is a
matter of admiration and wonder to every one.
Sunlight is by a thousand circumstances widely
and uniformly dihused, making 1t more accept
able to the eye, and during its journey TO earth
ii undergoes an important modification, for In
passing through tho mir II is deprived OF some OF
the red rays, while tho blue rays pass on-a cir.
cumstance which explains the azure character
OF the sky. In view OF these facts, 1t is Difficult:
to receive the theory with any seriousness that
because there may be a certain proportion OF
necessarily injurious. 1t would be q sorry thing
IL these same rays were forever filtered out OF
the light OF the sun by the medium OF
constant fog or cloud, as so often happens in the
days OF winter. Exposure to a purely elemen'
tary light. as red, yellow, or blue, does urdoubt.
cdly prove injurious either positively or mega
lively. The distress produced on working for
low light, as In the dark room of the photog'
rapher, who employs one or other Of these colors
on account OF their chemical inertness, Is well
known. Absence of sunlight Is held to be synon
ymous with the absence OF life, and the lfc-giv
Ing md invigOrating qualities OF solar light are
largely, IL not entirely. dependent upon the
chemically active, rays, and certain lines OF
phenomenon OF insulation going on day by day lft
would be uncomfortable and finally extinguished
White light, therefore,. as afforded in Its entire
ty by the sun, IL q necessity OF existence.