MEMORANDA. 4D 
this polariscope, the nozzle is placed at right angles to the 
screen, and the base-board is then clamped to the table. 
The front lenses of the magic-lantern are removed, the con- 
densers only being employed, and the source of light moved 
till a beam of parallel rays is produced; the lantern-nozzle 
is then pointed at the bundle till the rays are incident at the 
polarizing angle for glass, the proper direction being indicated 
for the uninitiated by a white lme marked on the frame- 
work, the right adjustment of parts being further indicated 
by the appearance of an even disc of light upon the screen. 
A design is then inserted in the large stage, its lines of con- 
struction focussed, the analysing prism inserted i in its jacket, 
and the coloured effect produéed and varied either by the 
rotation of the prism or the rotation of the design or 
crystal. 
By removing the panel from the support and placing it 
before a window, with nozzle pointing upwards, and adding a 
suitable power, it may be then used as a table polariscope, 
or the light of a reading-lamp may be employed as the source 
of light. 
By this simplification of parts, Mr. Highley is enabled to 
supply an instrument—which, for practical purposes, can 
hardly be surpassed for efficiency—at one half the price at 
which the gas polariscopes hitherto constructed have been 
sold. We fancy that many will appreciate this attempt to 
bring a costly instrument within the reach of experimentalists. 
