In my post of July 22, notice appeared regarding the exhibition of the
Southworth & Hawes "Parlor and Gallery Stereoscope" taking place in
Springfield in 1854.  Today's post mentions the exhibition of the
stereoscope at the (Boston) Athenžum two years later in 1854.

On this day (July 24) in the year 1852, the following article appeared 
in "To-Day: A Boston Literary Journal" Vol. 2 (July 24, 1852) pp. 55-
56:
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              THE STEREOSCOPE.

Mr. SOUTHWORTH has a large stereoscope arrangement of some 
daguerreotypes of the Laocošn, in the Athenžum Library in Boston, which 
is remarkably fine.  The illusion is absolute.  The spectator sees the 
copy of this celebrated group, in complete relief, standing off from 
the curtain behind it; and has nothing whatever to confirm his 
judgement, which informs him that he looks on reflections from a 
perfectly flat surface.
   Illustrations of the stereoscope, such as could be made by a few 
simple lines readily drawn, have been frequently repeated for some 
years past.  Any experimenter can make them, who will remember the 
difference between a one-eyed person and a man with two eyes.  If a 
one-eyed man looks on one object, he sees but one view of it.  A two-
eyed man sees two, which his judgement unites into one.  If the reader 
will make a drawing of a book near him as his right eye sees it, and 
another as his left eye sees it, he will see at once how different 
these two views are.  If, now, he will place these two drawings 
accurately before him, and look at them both with a dividing screen, so 
that Right Eye shall not see Left Drawing, nor Left Eye Right Drawing, 
he will produce the illusion of the stereoscope.  A one-eyed man has it 
always.  And here is one reason why, to give a certain picture-like 
effect to a piece of scenery, one frequently closes an eye in looking 
at it.  The application of this simple principle to two daguerreotypes 
of the same object, taken from points slightly apart, -- just as far 
apart as the pupils of two eyes, -- is a novelty, so far as we know, 
attempted first, within twelve months, by some English gentlemen.  Of 
course, the two daguerreotypes thus taken differ from each other, just 
as the two images seen by two eyes differ.  If, then, two eyes can be 
made to look at them, each seeing its own picture, there may be as 
completely the illusion of relief, as there is the sense of relief when 
two eyes look on the real object.  This is effected by setting the two 
daguerreotypes opposite each other, at right angles to the plane of 
vision.  In the plane of vision is a mirror, which reflects each -- 
taking the rays at an angle of 45 [degrees], and delivering them nearly 
parallel to each other -- to a spectator opposite it.  This spectator 
looks through two orifices; his Right Eye at the Right Eye's picture, 
his Left Eye at the Left.  And he sees, therefore, not a flat plate, 
but the complete representation of a raised surface.
   The effect of the Laocošn in this stereoscope is really finer than 
one often gains in looking at the statue; for the lights were carefully 
arranged for it, as they cannot always be commanded.  The metallic 
lustre of the silver is no disadvantage in the effect.  Curiously 
enough, the deception stops at a point which we should not have thought 
of.  The appearance is that of high relief; every muscle standing out, 
as in the statue, and the whole appearing at the proper distance from 
the curtain behind.  But there is, at the same time, an unmistakable 
feeling that there is only half a statue.  It seems as if it were a 
high relief, split from the wall.  Not that one could have seen the 
other half, but one is sure it is not there.  The whole looks as if it 
were only meant to be seen from the front.
   We have seen no explanation of this curious part of the illusion.  
We venture the following: --
   We are saved from this feeling, where the statue itself is the 
object of vision, by a series of rays from the very edges of the part 
visible, which grow up less and less distinct, till all are lost.  Some 
rays even will strike one side the pupil of the eye, which do not 
strike the other.  Hence that complete rounding, or varnishing, on an 
imperceptible line, not absolutely definable, which distinguishes the 
edge of a curved body, and which no painter grasps, or can.  Now, the 
daguerreotype is not as sensitive as the human eye.  These gradations 
are rendered by it in part, but more suddenly, with less precision and 
infinite subdivision than on the retina.  The edge is more defined, -- 
the profile of the statue more marked.  And there follows, of course, 
to the judgement of the spectator, the same opinion which he has when 
he looks at a full relief, split from the block which supported it.


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Posted for your enjoyment.     Gary W. Ewer     
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07-24-99