CARRARA MARBLE. 423 



" The granular limestone of Carrara is described by Hoffman as gradually passing into 

 compact fossiliferous Jurassic limestone, in such a manner that the connection between 

 their origin is unmistakable. He expresses his astonishment at meeting with clay slate, 

 mica slate, talcose slate and gneiss, situated in such positions as regards fossiliferous lime- 

 stone, as to leave no doubt of their connection, and of the simultaneity of their formation. 

 The slates not only follow immediately and regularly after the limestone, but alternate 

 with it, and pass into it, and blend with it so intimately, that the latter must be regarded 

 as unquestionably one of the sedimentary rocks. He considers it, as well as the slates and 

 gneiss, to have been metamorphosed by igneous action, and ascribes the result to the 

 protrusion of granite. But at the same time, he adds, that in this part of Italy scarcely 

 any granite occurs, although in this place the valleys are deep cut. 



"There can be no doubt that the marble of Carrara is a metamorphic rock; however, 

 this metamorphism has been effected not by imaginary granite, but by the action of water. 

 By this alteration the fossil remains have been obliterated," &c. 



In regard to granite in the vicinity of the Eolian limestone, we may say decidedly that 

 none occurs within any such distance as can by the most ultra- Plutonian be supposed to 

 have any connection with the metamorphism of the rock. On the west we must go into 

 the mountains of New York, and on the east to Ascutney on the Connecticut River, in 

 order to find granite. Small trap dikes do indeed occur in the limestone, but they affect 

 the rock only a few feet ; the metamorphism therefore must have been aqueous. 



The origination of the Carrara marble from rocks as new as the Jurassic or Oolitic, does 

 not prove that the Eolian limestone was derived from so recent a rock. But the fact 

 takes away all improbability from the supposition hinted at above, that this limestone 

 may be as new as the carboniferous limestone. 



On Ram Island, in Lake Champlain, we find a rock which is called silicious or flinty 

 slate, analogous to flint. We may as well say in this place, how such a rock might 

 be formed from calcareous slate. Says Bischof, " The conversion of calcareous slate 

 into hard porous stone indicates a penetration of silica and the displacement of carbonate 

 of lime by silica, which may be supposed to have taken place, since pseudomorphous 

 quartz with the form of calc-spar, does occur ; and it has already been sufficiently shown 

 that this alteration could take place only in the wet way." 



So far as our analyses have gone, although a few per cent, of magnesia occurs occasion- 

 ally in the Eolian limestone, yet it rarely contains enough to form the double carbonate 

 called dolomite. But the white limestones on the east side of the Green Mountains, in 

 the schists and gneiss, are almost all dolomite, as the Chemical Report shows. And this is 

 a general fact we believe in all places. But it has exceptions. Thus the beautiful white 

 limestone of Whitingham, in gneiss has 97 per cent, of carbonate of lime, and only 2 per 

 cent, of carbonate of magnesia. 



The mode in which such dolomites have been formed has not been explained exactly 

 alike by all chemical geologists. The fact, however, that the quantity of magnesia is much 

 smaller in less metamorphosed strata than in those where the change has reached its 

 maximum, shows, we think, that the dolomites of the schists and of gneiss have been 

 formed from pure carbonate of lime, which has been in some way produced in the process 

 of metamorphism. The old notions that it has been done by igneous fusion, or by the 



