92 PHYSIOGRAPHY. CLASS n. 



4. Rhombohedral Lime-haloide is a species widely dif- 

 fused in nature, and several of its compound varieties have 

 a considerable share in the constitution of mountains in 

 many countries. So they appear in Switzerland, Italy, 

 Carniola, Carinthia, Salzburg, Stiria, Austria, Bavaria, 

 Suabia, &c. The earthy varieties of chalk occur in the 

 low lands, or on the sea-shores of England, France, Den- 

 mark, Poland, &c. Beds of granular limestone occur in 

 gneiss, mica-slate, clay-slate, &c. ; beds of compact lime- 

 stone likewise in the grey wacke formation of the Hartz and 

 other districts, also associated with sandstone, &c. Of 

 crystallised varieties there are some, both simple and com- 

 pound, which are more frequently found in some countries 

 than in others. The most remarkable of them occur in 

 Derbyshire and Cumberland, in the mining districts of Sax- 

 ony and Bohemia, in the Hartz, in Carinthia, Stiria, Hun- 

 gary, France, and other countries. Iceland is the locality of 

 the purest and most transparent varieties, seldom crystallised 

 in the shape of regular six-sided prisms, and which have 

 by preference been called the doubly refracting spar. The 

 crystallised sandstone of Fontainebleau, in France, (Chaux 

 carlonatee quartzifere. H.), is a variety of rhombohedral 

 Lime-haloide, mechanically mixed with sand. If crystal- 

 lised, it assumes the form of the acute rhombohedron 

 R + 1 . Slate-spar occurs in Saxony, Norway, and Corn- 

 wall ; Pisolite near Laybach in Carniola, and at Carlsbad 

 in Bohemia ; Anthracolite in Salzburg, &c. Most of the 

 other varieties are so common, that it would be useless to 

 enter here into greater detail. According to the observa- 

 tions of Sir JAMES HALL, Mr BUCHOLZ, and others, car- 

 bonate of lime may be converted by the application of a 



columnar composition round a central axis in the belemnite 

 seems to depend upon a similar disposition of calcareous 

 matter in the living animal, similar perhaps to the fibrous 

 structure in the bone of sepia, perpendicular to the layers 

 of which it consists. H. 



