26 



POLARISATION OF LIGHT. 



small fragments of minerals placed be- polarised ray to pass along the resultant 

 tween prisms, in order to permit the axes. 



List of Minerals and Crystals, with the Character of their principal Axis and 

 the Inclination of their Resultant Axes. 



Character of 

 Principal Axis. 



Negative . 



Positive . . 



Negative . 



Negative . , 



Names of Minerals. 

 Glauberite 



Sulphate of Nickel, certain specimens 

 Nitrate of Potash 

 Mica, certain specimens . 



Carbonate of Strontites 

 Talc .... 



Carbonate of Lead . . 



Sulphate-carbonate of Lead . 

 Mother of Pearl . . . 



Hydrate of BaryteS . . . 



Mica, certain specimens . . 



Arragonite . . . 



Prussiate of Potash, certain specimens 

 Cymophane . . . 



Borax . . 



Anhydrite 



Apophyllite, biaxal . . . 



Sulphate of Magnesia . . 



-- Barytes . . . 

 Spermaceti . . . 

 Tincal, or Native Borax . 

 Nitrate of Zinc, estimated at about 

 Heulandite . . . 

 Sulphate of Nickel . . 

 Carbonate of Ammonia . . 

 Mica .... 

 Lepidolite ... 

 Benzoate of Ammonia . . 

 Sulphate of Zinc . . . 



- Magnesia and Soda . 

 Hopeite . . . 

 Sulphate of Ammonia . 

 Brazilian Topaz . . 

 Sugar . . 

 Sulphate of Strontites . 

 Murio-sulphate of Magnesia and Iron 

 Sulphate of Ammonia and Magnesia 

 Phosphate of Soda . . 

 Comptonite . . 

 Sulphate of Lime . . 

 Oxynitrate of Silver . 

 Dichroite . 

 Feldspar * 

 Topaz, Aberdeenshire . . 

 Sulphate of Potash . . 

 Carbonate of Soda . . 

 Acetate of Lead . . 

 Citric Acid . . . 

 Tartrate of Potash . . 

 Tartaric Acid . . . 

 Tartrate of Potash and Soda . 

 Carbonate of Potash . . 

 Kyanite ... 

 Hyper-oxymuriate of Potash . 

 Muriate of Copper . . 

 Epidote, about . . . 

 Peridot ... 

 Crystallised Cheltenham Salts . 

 Succinic Acid, estimated about 

 Sulphate of Iron, about . . 



Negative 



Negative 



Negative 



Negative 



Negative 



Negative 



Negative 



Negative 



Positive 



Positive 



Positive 



Positive 



Negative 



Negative 



Positive 



Positive 



Negative 



Positive 



Positive 



Negative 



Negative 



Negative 



Positive 



Negative 



Positive 



Negative 



Positive 



Positive 



Negative 



Positive 



Negative 



Positive 



Negative 



Positive 



Positive 



Positive 



Negative 



Negative 



Positive 



Positive 



Negative 



Negative 



Positive 



Negative 



Negative 



Positive 





 Positive 



Inclination of 

 Resultant Axes. 



2 or 3 

 . 3 



5 20' 

 . 6 



6 56 

 . 7 24 



10 35 

 . 10 35 



11 28 

 . 13 18 



14 



. 18 18 



19 34 



. 27 51 



28 42 

 . 28 7 



44 41 

 . 35 8 



37 24 



. 37 42 



37 40 



. 38 48 



40 



. 41 42 



42 



4 



43 24 

 45 

 45 

 45 





 8 



44 28 



46 49 



48 



49 42 



49 or 500 



50 0' 



50 



51 16 

 51 22 



55 20 



56 6 

 60 

 62 16 



62 50 



63 

 65 

 67 

 70 1 

 70 25 



70 29 



71 20 



79 



80 



80 30 



81 48 



82 

 84 30 

 84 29 



87 56 



88 14 

 90 

 90 



