Fig. 35. BIOT'S POLARISCOPE. 



THE MICROSCOPE. 



CHAPTEE V. 



MiCRoroLARiscopE : 69. Polarisation. 70. Condition of a polarised ray. 

 71. Polarisation by double refracting crystals. 72. Their effect 

 upon rays of light. 73. The micropolarisoope. THE MOUNTING OF 

 MICROSCOPES : 74. Conditions of efficient mounting. 75. Frauen- 

 hoffer's mounting. 76. Methods of varying the direction of the 

 body. CHEVALIER'S UNIVERSAL MICROSCOPE : 77. Mounting of this 

 instrument. 78. 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 65 



No. 114. 



