187 



some cases, the discs consist of eight or ten sectors of uniform thick- 

 ness, which become black in the plane of primitive polarization. 



The following is the author's list of substances giving circular 

 crystals. 



1. Positive Circular Crystals. 



Muriate of strontia. 



Sulphate of ammonia and magnesia. 



ammonia and cobalt. 



ammonia and iron. 



ammoniaand manganese. 



potash and zinc. 



red oxide of manganese. 

 Disulphate of mercury. 

 Hydrate of potash. 

 Citrate of jjotash. 

 Muriate of morphia, 

 magnesia. 



2. Negative Cir 



Borax in phosphoric acid. 



Lithoxanthate of ammonia. 



Oxal urate of ammonia, pure. 



Kreatine. 



Salicine. 



Asparagine. 



Manna. 



Parmeline. 



Palmine. 



Palmic acid. 



Esculine. 



Berberine. 



Cinchonine. 



Theine. 



Thionurate of ammonia. 



Carbazotate of potash. 



Hippuric acid. 



Sulphate of copper and iron, 

 and zinc, 

 magnesia and potash, 

 copper and ammonia 

 zinc and ammonia, 

 zinc. 



Substance in garnet. 



Stearine. * 



Stearic acid. 



Palmitic acid. 



Oil of mace. 



Almond soap. 



Starch. 



Substance in garnet. 



mica. 

 Mannite. 



Citrate of ammonia. 

 Myristic acid. 

 Cupreo-sulphate of potash. 

 Kreatinine. 



cular Crystals. 



Animal fat. 

 Cacao butter. 

 Hatchetine. 

 White wax. 

 Chrysoleptinic acid. 

 Succinate of zinc. 

 Chromic acid. 

 Citric acid. 

 Nitrate of uranium. 



urea. 



brucine. 



strychnine. 

 Grallic acid. 



Sulphuret (nitrate) of cadmium. 

 Suiphuret of potassium. 

 Santonine. 

 Acetate of strontia. 



quinine. 

 Chloride of zinc. 

 Oxide of uranium. 

 Protoxide of nickel. 

 Phosphate of nickel. 

 Carbonate of nickel. 

 Substance in mica. 

 Adipocere. 

 Margaric acid. 

 Ethal. 



