SOME EFFECTS OF LIMESTONE. 57 



which occur so abundantly in Berkshire county, and which are so generally known as marble, 

 important localities of which exist at Stockbridge, Lanesborotigh, New-Ashford, Adams, 

 Egremont, and which in fact lie along the whole western face of the Green Mountains. 



Notice of some of the peculiar effects which the limestone appears to hace produced on some 



of the minerals imbedded in it. 



I do not so much propose to make out an argument for establishing the doctrine under con- 

 sideration, as to present the curious facts of the case. I had, on my first visit to Rossic in 

 1836, noticed a singular variety of quartz in the limestone which occurs there in abuiulaiicc, 

 which appeared to have been softened by heat, or partiall}' fused. It is usually in the form 

 common to the species, but imperfect ; the solid angles of the crystals being rounded, and 

 sometimes the termination is drawn out like a piece of melted glass, into a sharp point. In 

 other instances, the quartz presents no appearance of crystallization, but it is rounded and 

 frequently wrinkled, as if bent while in a soft or pasty state ; in fine, the)'' have all the ap- 

 pearance of silicious slags from a furnace, some much more so than others, but all partake of 

 the character. Sometimes a crystal appears to have been stuck into another while it was soft. 

 The most puzzling circumstance is the apparent fusion of a mass of cjuarlz upon a crystal of 

 feldspar : a rounded mass, though somewhat flattened, appears to be pressed directlj" upon 

 the feldspar, lying still upon the surface, but in some instances penetrating into a fissure in 

 the crystal. The difficult point for solution, is that the quartz appears to have been softened, 

 while the feldspar, much more fusible, preserves still the sharp corners of the crystal. Ad- 

 mitting the fact of fusion, I see no way to explain the phenomena, but to suppose that feld- 

 spar, being more fusible, its particles become perfectly mobile, and recrystallize on cooling ; 

 and the quartz being merely softened, does not crystallize, but remains in the condition of a 

 slag. These effects, however, do not stop here : the crystals of phosphate of lime present 

 appearances much the same as quartz, their solid angles being rounded, smooth and vitreous, 

 and many impressions upon their faces being like the impress of some body, as the end of a 

 finger, when soft. In all the crystals from this locality, there are rounded cavities, or else 

 spaces filled with calcareous spar. In no instance are those cavities angular ; they appear in 

 this respect like those in amygdaloid, which are often filled with the same substance. 



All of these facts are inexplicable, except on the ground assumed, that they have been 

 exposed, while in their beds, to a partial fusion, and at a period too subsequent to their original 

 formation. Whether this is the true explanation or not, it is the only one which I can offer 

 which explains with some degree of probability at least the phenomena in question. Some of 

 the crystals of phosphate of lime are perforated with holes about the size of a pin ; these are 

 more angular than the larger. In the centre of a crystal, it is very common to find a large 

 cavity or space in which the continuity of the phosphate of lime is "broken, without any com- 

 munication existing with the outside of the crystal. Sometimes it is filled with a globule of 

 quartz instead of lime ; and when those oval masses are removed, they present upon the 

 outside the vitreous lustre. 



Geol. 2d Dist. 8 



