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POPULAK SCIENCE REVIEW. 
cellent Microscope and its Kevelations.” We select a few of the 
salts mentioned there : — Arseniate of potassa^ chlorate of soda, 
©hi orate of potassa, bichloride of mercury, citric acid, chloride 
of cobalt, chromate of potassa, bichromate of potassa, borate of 
soda, nitrate of soda, oxalate of ammonia, oxalic acid, sulphate 
of soda, sulphate of potassa, sulphate of copper ammoniated, 
tartrate of potassa. 
Grreat advantage is gained sometimes by examining trans- 
parent, vegetable, and animal objects by polarized light, the 
result being to give the effect of perspective by rendering the 
thicker portions of the substance bright. 
Space does not allow of more than a reference to another set 
of beautiful experiments to be made with the polariscope. Griass 
under pressure or strain, directly applied, or indirectly by heat- 
ing and rapidly cooling, or by partially heating, possesses 
the power of double refraction, and beautiful fringes of inter- 
ference are seen on looking at it in a polarizing apparatus. For 
an account of these experiments we refer to the works of Sir 
J. Herschel, before referred to. 
