X)F THE FAROE ISLANDS. '261 



the sides of which would measure about 67". This is 

 the Mesotype epointee, fig. 175. of Hauy. 



2. The same crystal, with the apices of the pyramids perfect ; 



may be termed the Pyramidal Apophyllite. 



3. When the same crystal is so short in the prism, that the 



truncating faces touch, and so broad on the terrtiinal 

 faces, as to reach the sides of the prism, a cube trun- 

 cated on all the solid angles is produced. 



4. In rectangular prisms, hollow, and diverging at the termi- 



nation. This variety, I suspect, owes its present ap- 

 pearance to decomposition. 



In one specimen, I found some of the crystals of zeo- 

 lite covered with a sheath of calcedony, open at the top, 

 and partly hollow, owing to the decomposition of the apophyl- 

 lite. It would be almost endless to proceed, with a detail 

 of all the peculiarities which ocpur, in the combinations of these 

 different substances. I have said enough to mark several cu- 

 rious circumstances relating to them ; many of which will per- 

 haps have an effect quite the reverse of affording any clew to- 

 wards those hidden arts by which the hand of nature has ac- 

 complished their formation. We have proofs, most unequivo- 

 cal, of the igneous origin of the rock in which they are imbed- 

 ded, and consequently of their own. But granting this, as also 

 the construction of the cavities, and the production of the sta- 

 lactites of calcedony, whence came the second coating, which 

 so frequently occurs, lining them entirely and uniformly 

 throughout ? whence the different alternations of quartz and 

 calcedony ? and whence the substance of those beautiful crys- 

 tallizations of zeolite I have just mentioned ? 



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