102 Wheatstone on the Binocular Microscope, Sfc. 
pseudoscopic, though he describes one which, had it been 
made, would have been stereoscopic ; he was, however, quite 
unaware that there would be any difference of this kind between 
them. The pseudoscopic effects when inverted images are 
presented, and the natural appearances when erecting eye- 
pieces are employed, have not escaped the observation of Mr. 
Riddell. 
Besides actual inspection by means of the binocular micro- 
scope, there is another way in which the advantages of bino- 
cular vision may be applied to microscopic objects. The 
beautiful specimens of photography, reproducing the highly 
magnified images of objects, inserted in a recent number of 
the Microscopic Journal, makes one regret that they were not 
accompanied by their stereoscopic complements. A very 
simple modification of the usual microscope would fit it for 
producing the two pictures at the proper angles ; all that is 
necessary is to cause the tube of the microscope to move inde- 
pendently of the fixed stand round an axis, the imaginary pro- 
longation of which should pass through the object. A motion 
of 15° would include every difference of relief which it would 
be desirable to have, and it is indifferent in what direction this 
motion is made in respect to the stand. The pair of stereo- 
scopic pictures may be obtained by a still simpler method, 
which requires no alteration in the microscope ; the object 
itself may be turned round on an imaginary axis within itself, 
from 7° to Ib^. But this method is inapplicable unless the 
light be perfectly diffused and uniform so as to avoid all 
shadows, the presence of which would give rise to false stereo- 
scopic appearances. In the former case, where the object 
remains stationary and the tube moves independently of the 
frame, the arrangement of the light so as to cast single shadows 
might be an advantage, and assist the visual judgment. 
