CRYSTALS CONTAINING FLUID. 185 



of 30° at 50° Fahr. On exposure to the air, it undergoes 

 quick motions and changes, and finally evaporates, leaving 

 a residue of minute solid particles, which, from the moisture 

 of the hand alone, suddenly become fluid again ; the re- 

 sidue volatilizes by heat, and dissolves in acids without 

 eff'ervescence. 



'' The other fluid, which is sometimes found with Brew- 

 stoline, has been named Cryptoline, from the Greek word 

 'kryptos,' concealed. This liquid, when exposed to the 

 air, speedily hardens into a yellowish, transparent, resi- 

 nous body, not volatilizable by heat, or soluble in alcohol 

 or water, but dissolving rapidly, with efi'ervescence, in 

 sulphuric acid. Nitric and hydrochloric acids also dis- 

 solve it. The index of refraction is nearly the same as 

 that of water.^^ 



No satisfactory explanation has been given of the 

 presence of this orgauic fluid. These fluids were first 

 discovered in quartz, topaz, chrysoberyl from Quebec, 

 and in amethyst from Siberia. Since this discovery. Sir 

 David has examined many hundreds of specimens of to- 

 paz by the aid of the microscope and polarized light, and 

 discovered many cavities, filled with crystals of various 

 primitive forms and with different physical properties. 

 These crystals are either fixed or moveable ; some of them 

 have their axis of double refraction coincident with those 

 of the specimen which contains them. Some of these 

 crystals melt by the application of heat, and recrystallize 

 on cooling ; others do not recover their crystalline form 

 again ; others resist the most powerful heat. During the 

 examination of a diamond. Sir David found a small cavity 

 which, when seen by polarized light, exhibited four lumi- 

 nous sectors; this appeared to prove that the diamond, 

 when in a soft state, had been compressed by an elastic 

 force proceeding from the cavity. This inference counte- 

 nances the opinion that the diamond was of vegetable 



