Notice of a Scientific Expedition. 



347 



its usual form of corrspound masses of individuals radiating from a 

 common centre. Intermixed is the wine colored carbonate of 

 lime. The specimens are exceeding rich and vie in beauty with 

 minerals of the same kind from the deep mines of Europe. 



Calcareous Spar. — The more common forms of this substance, 

 are the primary, the chaux carbonatee inverse of Haiiy, and the me- 

 tastatique. The inverse, somewhat elongated, forms a remarkable 

 variety of intersected or hemitropic crystals. 



Figs. 1 and 2, are the most common of the simple forms. Oc- 

 casionally, however, they form hemitropes. The manner in which 

 these are found, may be understood supposing the faces a, a, joined 

 in composition with their similar edges parallel, or rather forming 

 one continuous hne. Now if these crystals thus applied, are made 

 to perform an angle of revolution equal to 180°, the hemitropes as 

 Figs. 3 and 4, will be produced. This is one kind, and is of cora- 



1 and 2. 



Figs. 3 and 4. 



mon occurrence, but it more frequently happens that two of these 

 hemitropes are joined or connected together in composition, and 

 form by this union the remarkable intersected 

 or double hemitropes as in Fig. 5. Often the 

 last described hemitropes become more com- 

 plex by embracing another crystal within the 

 angle b, b. 



All the forrris and varieties mentioned 

 above, are found frequently in one specimen. 



Patridge Island, is the only locality which 

 furnishes these peculiar and interesting forms. 

 It ought to be remarked, however, that at 

 Cape Sharp, the same may be found, as fine 

 specimens of wine colored spar, are known to occur there. 



