CALCIFEROUS GROUP. 33 



with anthracite coal, the latter substance often existing within the crystals. The crystals 

 occur in the cavities of the rock: these cavities are usually very irregular as to form, and 

 differ greatly in size, varying from mocroscopic to a yard in diameter. With these two pro- 

 ducts, i. e. crystals of quartz and anthracite, we often find lamellar carbonate of lime, rhombic 

 crystals of the same, and also magnesian carbonate of lime," the latter in rhombic crystals also. 

 The shattered conditon of the rock, and its loose texture generally, show the extent of chemi- 

 cal action to which it was subjected ; its composition and its position in the series, being upon 

 the -primary mass, highly favoring that action. 



The Noses, Little-Falls and Middleville, are the three best localities for these products, 

 though they are found at numerous others, as stated in the Report of Dr. Beck. 



At Spraker's Basin, the parts containing the crystals are not far below the fucoidal layers. 

 Some of the cavities show, first a lining of lamellar carbonate of lime ; then a deposit of 

 anthracite, in parts intermixed with that mineral, and then the quartz crystals. In others 

 quartz crystals line the cavities in part ; the anthracite being mixed up with it, and covering 

 the surface, which shows a depression towards the centre. 



At Little-Falls, the cavities are very numerous, but small, the crystals of quartz often lining 

 the cavities ; the rhombic crystals, usually of magnesian carbonate of lime, adhering to the 

 crystals. Numerous cavities also exist, whose sides are covered with anthracite in a state 

 resembling dust ; and in others, this substance is seen, having the appearance which we would 

 suppose it would assume, were a few drops in a highly fluid state to fall upon the bottom of 

 the cavity, and then congeal. Specimens of this kind are common in the small cavities of the 

 rock thrown out in enlarging the canal, to the west of Little-Falls, not far below the first 

 lock from the village. 



At Middleville, the large cavities are in greater number, the rock crystals are more abun- 

 dant, and more perfect as to form and limpidity, than in any other known locality. A greater 

 proportion of anthracite has also been found associated with them at that place ; the quantity, 

 however, hardly sufficing to meet the demand for cabinet specimens. 



Some of the cavities have been knowm to yield nearly a half a bushel of crystals. When 

 so large, the rock is more porous or loose in its texture, and the crystals less perfect as to 

 form and clearness. The more compact the rock, and the fewer the crystals, the more per- 

 fect they are in all respects. In some of the cavities, a coating of coal has been found, cover- 

 ing the crystals ; they occupying the lower part, and the surface of the coal depressed towards 

 the centre, showing that it had been soft, or in a yielding state. In breaking into a cavity, 

 an explosion sometimes takes place, probably owing to a partial vacuum, into which the air 

 rushes to restore the lost equihbrium on being fractured. 



The fact long observed elsewhere, has been remarked here, that the crystals of the same 

 cavity have usually one and all a common family resemblance, and differ from those of another 

 cavity, should the cavities differ as to form ; the sides of the cavities exerting an influence 

 upon the forming crystals. These crystals are much sought for, as objects to gratify taste, 

 and as beautiful specimens of mineralogy. 



Geol. 3d Dist. 5 



