Fig. 35.— Biot’s Polariscope. 
THE MICROSCOPE. 
-♦-- 
CHAPTEE Y. 
Micropolariscope : 69. Polarisation.— 70. Condition of a polarised ray. 
—71. Polarisation by double refracting crystals.— 72. Their effect 
upon rays of light.— 73. The micropolariscope. The mounting of 
microscopes : 74. Conditions of efficient mounting.— 75. Frauen- 
lioffer’s mounting.— 76. Methods of varying the direction of the 
body. Chevalier’s universal microscope : 77. Mounting of this 
instrument. —7 8 . Method of rendering it vertical.— 79. Method of 
adapting it to the view of chemical phenomena. —80. Method of 
condensing the light upon the object. Ross’s improved microscope : 
81. Useful labours of Mr. Ross. —82. Details of his improved 
microscope. 
THE MICRO-POLARISCOPE. 
69. When a ray of light has been reflected from the surface of 
a body under certain special conditions, or transmitted through 
certain transparent crystals, it undergoes a remarkable change in 
its properties, so that it will no longer be subject to the same 
effects of reflection and refraction as before. The effect thus 
produced upon it, has been called polarisation, and the ray or 
rays of light thus affected are said to be polarised. 
Lardner’s Museum of Science. f 
No. 114. 
65 
