1847,] The Limestones, and Lime. 77 



in New York and Vermont, or that part which is widely known 

 as the Green Mountains, in the northern extremity of the United 

 States, which being traced southwardly merges itself in the great 

 Appalachian chain. The magnesian limestone is near the 

 primary, and is generally know^n as the Stockbridge lime- 

 stone. The sparry limestone, in which we have not detected 

 magnesia, except in inconsiderable quantities, ranges on the 

 west side of the Stockbridge limestone and occupies a parallel 

 position to it, and may be distinguished by its numerous short 

 sparry interrupted veins of a more crystalline structure than the 

 body of the rock. It is frequently slaty and imperfectly accre- 

 tionary, while the Stockbridge in its purest and most perfect form 

 is a crystalline sacharoidal rock, which is susceptible of a fine 

 polish, and constitutes one of our finest marbles; some beds, for a 

 limited extent, having been found nearly equal to the Italian 

 statuary marble. The composition of the Stockbridge limestone 

 is not uniform; that is, omitting to notice some minor differences 

 which concern merely the quantity of alumina and iron; it is 

 found to differ still more in the quantity of magnesia which it 

 contains. Even many beds which have passed for dolomite, have 

 proved, on analysis, to be a pure carbonate of lime. Still it is so 

 common for the friable limestones to contain magnesia, that we 

 are rather disappointed if we fail in detecting it in them. 



The limestones of this system are usually distinctly stratified; 

 beds, however, of a limited extent appear destitute of the lines of 

 stratification. So it often happens in well known sedimentary 

 rocks, which when homogeneous, seem to consist of thick masses 

 formed of materials uniformly distributed through them, and des- 

 titute of those peculiar lines which denote stratification. The 

 color of these limestones are white, gray, mottled or clouded. 

 The clouded portions are mixtures of carbonate of lime and fine 

 particles of the adjacent slate rocks, and is never due to the oxide 

 of iron or manganese, and hence those clouded varieties retain un- 

 changed the colors which they exhibit at the time they are 

 removed from their beds. We leave out of view here, the stains 

 which appear in some of the finest varieties which are produced 

 by sulphuret of iron, and which totally destroy their beauty and 

 usefulness. The limestones of this system are found in New York, 

 Connecticut, Rhode Island, Massachusetts, Vermont, and Maine; 

 and we have before us analyses, from many localities from each of 

 these States. The formation or system extends also through the 

 Southern States, but we have no good analyses of them in their 

 prolongation south. 



