The herald., 1897-08-15
Effects of Light and Heat

Many interesting facts regarding tan
and sunburn have been developed by
modern scientific observation. One of
the most surprising is that it is sunlight
and not heat which affects the skin.
That severe sunburn may be produced
without heat has been proved by the fact
that persons exposed to strong sunlight
on the tops of mountains, at extremely
low temperatures, have been burned
just as if they had undergone the suns
heat as well. Alpine travellers and al
who have taken long journeys over the
snow have had the experience of being
painfully burned by the reflected light
from the white, glittering surface, and
sunburn from reflections on the water is
equally we'll known. That heat alone
does not produce the effect is clear from
many evidences. Persons exposed to the
high temperatures which prevail in the
firerooms of ocean steamers, in deep
mines and other places, do not become
tanned and burned in the same manner
as those who work in the sun. Accord
ing to the present theory, then, sunburn.
or tan, is produced by the actinic rays of
the suns light--that is, those rays which
possess the power Of affecting chemical
ly certain substances upon which they
fall
That part of the skin which receives
the chemical action of the light rays so
as to produce sunburn, tan or freckles,
is the pigment of coloring matter. This
varies greatly in sensitivenesS in diff
ferent persons, not always being gov
erned by the complexion, although as
rule, blondes and redhaired persons are
more subject to sunburn than others.
Just why some people burn red while
Others freckle or tan, does not seem to
be definitely known; doctors usually
say that the difference is due merely to
the varying qualities of skins. General
ly, after months of exposure to the sur,
any Skin becomes hardened to its effects,
takes on a permanent brown or bronze
color, and is not changed thereafter by
| any amount of additional exposure.
"The darkening of pigment in the
skn," said a physician, is an effort of
nature to frterpose a defense against
the infaming light rays. The darker
the surface upon which they fall the
more difficult is it for them to pass
through and injure the sensitive parts
beneath. Sunburn, however, does not do
light and air are rather beneficial than
otherwise although the first effect, if
there Is swelling and extreme heat, is
rather painful"
When. asked why wind often seemed
to produce burn as readily as sunlight
the doctor said: 1.-The wind, by irritat-
ing the skin, produces certain amount
of congestion-and thus predisposes TO
the effect of the sunlight. When the
skin is even slightly congested, 1t will
burn quickly, even in rather weak light.
In the same way, heat also, by con ges*-
ing the skin, is predisposing cause TO
sunbuIn, though not the direct cause,
which is to be found in the light"
In connection with the subject of the
effect of light upon the skin, it is inter-
esting to recall many cases in which the
Roentgen rays have caused something
almost precisely like sunburn. Persons
who have exposed their hands or any
part of their bodies for a considerable
length of time to the powerful electric
rays have observed the sensations and
compared them to an acute form of burn
from sunlight. 1t seems to point to Il
close rela ationship between the two, and
to support the modern theory of sun
burn here described.