The sun. [volume] (New York [N.Y.]) 1833-1916, 1903-08-30

1
animals. and even horses and cats. appreciate
..ays that are not luminous and are invisible
In Us IN me ordinary spectrum are ths
luminous Colored rays. which combined make
Mnite light When returned TO the eye from
,enee,hn4 surfaces some OF the coi9red rays
nn0ay pc absorbed. and those which are re-
necteu produce impressions or color. Inns
ocCurE' also, when certain colors are aD-
ssorpcu by transparent media. In ADDITION
10 the luminous rays are invisible heat rays
ana invisible chemical rays. Those chemical
IhEs winch act on Photographic surfaces are
caled actinic, Beyond the visible spectrum,
especially at the violet end. are INVISIBLE
actlnlc rays, We must take account, also.
o thc s0-called cathode rays emanating from
.hr cathode, when current from an N;
duetlon coil is passed through a partial
tanned by decomposition Of the cathode rays.
we nave, in addition what are called Bee
Hnorei rqys. .manating from spbstnncsss
inylsibl" rays in the dark, this continuing.
4 Is supposed, for months and even for years.
Inc recent discovery of radium makes US
acquainted with invisible rays coming from
this and other radioactive substances. which
are given OFF for an indefinite time. All
these rays will act on II Photographic MIN:
and many of them will pass through opaque
substances but are arrested by glass. IL
H. known that the ordinary actinc rays are
Of very short wave length, and the wave
lengths of the cathode rays, the X-rnys, and
rays from radioactive elements are assumed
TO be even shorter, The latter, including the
cathode and Mays 1t Is thought on account
cannot be reflected or rcfraCtcd and will pass
through certain substances impervous TO
luminous rays, Al these rnys not only &C;
on Photographic film. but have marked
effects on living TISSUES,
All the rays mentioned. both visible and
Invisible, may be changed in their wave
lengths by certain substances and are then
given off in different colors. This, is known
as finoresCenCe. and II occurs only during
exposure Al the invisible rays may be
converted into visible rays by this same
tInnrpAt'pnrp lnSnlVlnH
in wave lengths.
Certain substances give of fnc ' ;.
rays in the dark for a., Considerable tune
known as phosphorescence. " * thought by
some physicists that the peculiar light COM
ing from the eyes of nocturnal animals IN
1T has been observed that the human skin
will give on invisible rays acting on photo
graphic film; and, indeed, it Is difficult to say
what substances may not absorb ana store
mp luminous or actinic rays and give OH m
visible rays possessing chemical activity
This Is not a severely scientific article:
here ideas which may seem visionary in
sense not intended to be conveyed by its
title. acknowledging my reflections 70 be
scientific basis. With this explanation and
provision, ! trust | may DO INDUCED in the
following thoughts
observations on the comparative sensiblliiy
Of tho retina in nocturnal animals and IN
animals endowed with what may maybe be called
was extracted from the rctina of the frog
by Boil. in 1879. kIhne and Others have
since observed 1t in mammals and in man.
II has been found possible to nix ages
of simple objects, such US strips Of black
paper pasted on plate OF ground glass.
upon the retina by a process very like pho
Biography. When the invisible aCtinic rays
were discovered, they were found to come
directly from the sun or from certain bodies
actually incandcscent or luminous, although
they exist, as wei; BEYOND the visible IN 5peSf, ,
rays. the N-rays and the rays from radio
active substances, all acting on photo
graphic hlm and AZ capable OF exciting nnor.
of these rays will not penetrate glass. but
some will penetrate rock salt and trans
parent quartz.
know Of no comparative observations
on the permcabiity TO light Of the transparent
media Of man and Of nocturnal animals, IL
seems to me not Impossible that the eve in
nocturnal animals may admit ravs that are
invisible 10 US. The sensation Of brightness
is said to depend on the amplitude of lIni-
nous oscillations and color TO depend on
their frequency. 1t Is generally admitted
that invisible rays are Of almost nConccivably
short wave lengths: but they may be mad"
to change their wave lengths, and thus be
that the perception of light and ColOrI Ii du" to
the stimulation Of structures in the relina,
possibly producing vibrations Corr"spoudin@
in some wnv with the waves OF light that the
waves OF invisible rays are 50 short that they
cannot be- reflected, reira cted or polari2ed:
and certainly, as they are invisible to us.
they are not perceived by means OF IN" hu-
man retina
II seems 10 me possible that certain rays
may penetrate the eyes OF some OF the lower
animals. which cannot enter the eve OF nlnn:
and that such animals may possess anatOml-
cal elements in the rrtna sensitive to ThyS
which give us, no visual impression, these
rays being radiated from many objects in
otlsCurity Observations have lately been
made on the structure of the sensitive layer
of the retlna in nocturnal animals: and 1t
appears from these researches which are
mainly anatomical the structures trOdsl
absorbing visual purple are unusually abun-
dant and are Of unusual length, and that the
quantity Of purple which they contain -
unusually large won krirsI. II is generally
admitted that visual purpl" adapS the eve
To vision at low intensity. When We say
that nocturnal animals see in the dark. We
mean in obscurty. for IT i, hy no means totally
dark. even in the darkest night Animals
that live in total darkness, aS IN the depths
they have actually no ornnns Of VISION
while many so-Cacd nocturnal animals
present extraordinary development of the
Possibly, rays invisible 10 us and not
capable of penetrating the human eye are
emitted al night by multitude OF objects
Possibly, invisible rays, of excessive short
wave lengths, are appreciated by peculiarly
sensitive elements Of the retina in these
animals. Possibly, these are converted into
longer waves by iiuorescence. and the light
given on by the eyes Mt might is huorescen,.
Possibly, a change of invisible into visible
rays which is the essence. of iiuorescence
excited by invisible rays-iS an important
element in perception by the dark adapted
eye. A. regards invisible rays. if they cam
not he reflected, refracted or pOlarizcd. and
If they do not pnSs through an object. they
must be absorbed: and they certainly hnve
soWe sort of chemical action and must make
some kind Of an impression on sensible parts.
Perhaps these are reasons why some animals
can what call the dark