Bauhaus-Universität Weimar

Marietta Apparatus Company: Psychological Equipment, Marietta, Ohio, II
0 26.00 
V8001 Hering Falling Beads Apparatus. - 
Fig.44 The observer looks through a tube and slit into a box which 
is open on both sides. In the box there is set up at any- 
desired distance a little standard with a white knob which 
stands out clearly against the background* While the eye is 
fixed on this, beads are allowed to drop through the small 
holes which are arranged one centimeter apart in the cover 
of the box, and in each case the observer is to decide whether 
the bead has fallen in front of or behind the knob. The 
purpose of using falling beads instead of fixed objects is 
to avoid parallactical displacements such as would occrir in 
case of movements of the head and eyes. Since moreover the 
beads are different in size, the only criterion for determining 
the distance of the falling bead from the knob, when one eye 
is used for observation, is the degree of clearness, whereas 
disparation comes into play when both eyes are used. Since 
one’s judgment is correct when both eyes are used, biit very 
uncertain and often absolutely incorrect when one eye is used, 
the experiment shows in a clear way the importance of binocular 
vision for the determination of depth. 
V8002 Hillebrand Edge Apparatus, - - $ 64.00. 
The purpose of the apparatus is to present to the eye 
objects at different distances in such a way that the judgment 
of the distance is possible only on the basis of accommodation. 
On a horizontal flat base there is fixed a short vertical 
axis about which revolve two horizontal arms. On these arms, 
slides carry vertical screens. The inner vertical edges of 
these two screens, which are the objects that are to be judged 
as to distance, are sharp and exactly parallel thus excluding 
all secondary clues to the determination of depth. The eye of 
the observer is over the center of rotation of the two arms, 
and looks through a short removable tube with an elliptical 
opening toward the front. The tupe is placed in a screen which 
conceals the other parts of the apparatus* The background is 
formed by the frosted glass which is illuminated by lamps. The 
two arms are so joined by a curved piece at the far end that, 
when they are turned the edge of one screen comes into the field 
of vision at the very instant when the edge of the other screen 
has left it. In this way a quick change of the two objects can 
be brought about. 
V8101 Reflection Stereoscope, Wheatstone, Simple model. 
Fig.35-3 Consists of a pair of vertical mirrors set at an appropriate 
Fig.35-4 angle, and a pair of vertical support frames for carrying 
the stereoscopic cards. - - y 37.00. 
V8102 Reflection Stereoscope, modified by Hering. (Known as the 
Mirror Haploscope.) A more elaborate model of the Wheatstone 
principle. - - - 0125.00. 
V8103 Demonstration Reflection Stereoscope, (Titchener’s combined 
Fig.40. Storooscope, Telestereoscope and Pseudoscope) - v 75.00. 
V8104 Refraction Stereoscope, Brewster, Simple form. - 0 2.00. 
Refraction Stereoscope, Removable partition 


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