I. On the Existence of Two New Fluids in the Cavities of Mine- 

 rals, which are immiscible, and possess remarkable Physical 

 Properties. By DAVID BREWSTER^ LL.D. F. R. S. Lond. & 



Sec. R. S. Edin. 



TER. 



' ' 



(Read March 3. and 17. 182SJ 



JLN the year 1818, my attention was accidentally directed to the 

 subject of water in crystallised bodies, by the explosion of a crys- 

 tal of Topaz, which I had exposed to a red heat, for the pur- 

 pose of expelling its colouring matter. This violent disruption 

 of the specimen, which was shivered into a thousand films, of ex- 

 treme tenuity, arose from the expansion of the imprisoned fluid, 

 and induced me to institute a series of experiments, for the pur- 

 pose of determining the nature of the fluid, the form of the cavi- 

 ties which contained it, and the arrangement of these cavities in 

 reference to the crystalline form of the mineral *. 



Small portions of fluid had been long ago observed by mine- 

 ralogists in Topaz, Rock-Crystal, and Fluor-Spar. Mr SIVRIGHT 

 found them also in Calcareous Spar, Sulphate ofBarytes, and Sul- 

 phate of Lime; and I detected them in the Emerald, in Beryl, 



* An account of these experiments was announced for publication in 1819, in 

 the 1st Number of the Edinburgh Philosophical Journal; but the desire of ob- 

 taining more general results prevented me from publishing it at that time. 



VOL. X. P. I. 



