FORMATION OF CRYSTALS. 



729 



sliown on a, red selenite ground, Ciystallisation under a 

 somewhat different condition and combination is seen in 

 the New Red Sandstone, ]S^o. 158. 



The prismatic rings of another crystalline substance, 

 Quartz, represented in ]N'o. 159, possess great interest. 

 Again, that of Arragonite, Tremolite, and (jarbonate of 

 Lime. The latter is frequently seen in combination with 

 animal structure, and is then productive of many re- 

 markable changes and modifications, such as we have 

 represented in Plate VIII. :N'os. 171, 172, 175, and 180, 

 all of which should be prepared for examination with as 

 well as without the polariscope. 



The formation of artificial crystal may be readily 

 effected, and the process watched, under the microscope, by 

 simiDly placing a drop of a saturated solution of any salt 

 upon a previously warmed slip of glass. The following 

 list of salts and other substances form a beautiful series 

 of objects for polarised light : — 



Alum. 

 Asi^ai-agine. 



Aspartic Acid. Plate VIII. No 

 Bitartrate of Ammonia. 

 Boracic Acid. 



Borax. Plate VIII. No. 164. 

 Carbonate of Lime. 

 ,, Soda. 



Chlorate of Potash. 

 Cliloride of Barium. 

 „ Cobalt. 



„ Copper and Ammonia 



,, Sodium. 



Cholesterine. 

 Chromate of Potash. 

 Cinchonine. 

 Cinchonidine. 

 Citric Acid. 

 Hippuric Acid. 

 Iodide of Mercury. 



,, Potas.sium. 



,, Quinine, 

 lodo-disulphate of Quinine. 

 Murexide. 

 Nitrate of Bismuth. 



, , Bar jles. 



,, Brucine. 



,, Copper. 



,, Potash. 



,, Strontian. 



,, Uranium. 

 Oxalate of Ammonia. 



„ Chromium. 



,, Chromium and Potash. 



,, Lime. 



,, Soda. 



Oxalic Acid. 

 Oxalurate of Ammonia. 

 IGS. ! Permanganate of Potash. 



Phosphate of Lead and Soda. 



Platino-cyanide of Magnesia. 



Plumose Quinidine. 



Prussiate of Potash, red and yellow. 



Quinidine. 



Santonine. 



Salicine. 



Salignine. Plate VIIL No. 1C2. 



Sulpliate of Cadmium. 



,, Copper. 



„ Copper and Potash. 



Sulphate of I ron. 



„ Iron, Cobalt, and Nickel. 



,, Magnesia. 



,, Nickel and Potash. 



,, Soda. 



,, Zinc. 



Sugar. 



Tartaiic Acid. 

 Thionurate of Ammonia. 

 Triple Phos])hate. 

 Urate of .Ammonia. 



,, Soda. 

 Urea, and all the urinary deposits. 

 Uric Acid. 



MINERALS. 



Agates, various. 

 Asbestiform Serpentine. 

 Avanturine. 

 Carbonate of Lime. 

 Carrara Marble. 



