OF THE TACONIC SYSTEM. 107 



§ 2. Marbles. 



The Stockbridge limestone furnishes by far the greatest amount of the native marbles 

 used in the I nited Slates. The most esteemed is the clear white marble with translu- 

 cent edges. It is not difficult to procure pieces which are faced, as it were, with this 

 variety : but thick slabs, free from clouds, are rare. The larger proportion of the varieties 

 appertains to the clouded kinds, which vary greatly in the patterns furnished by different 

 beds. 



It will be needless to furnish statistics of the trade in this material. The principal facts 

 which I wish to speak of, are that the white and clouded marbles in our different markets 

 are raised from beds in the Stockbridge limestone ; that these beds are coextensive with 

 the Taconic system ; and hence, in a practical view, we are to search for these marbles 

 along the general range of this system, and nearer to the great primary schists in New- 

 York, Massachusetts and Vermont, than to the western border of the system. 



Mr. Brown, the sculptor, now residing in Italy, tested the marble of some of the beds 

 in the neighborhood of Middlebury (Vermont) , for the purposes of statuary, and pro- 

 nounced it very good ; but in consequence of his removal soon after, its qualities have not 

 been sufficiently investigated, or the quarries sufficiently exposed to determine their extent. 



§ 3. Roofing slate. 



The beds of roofing slate quarried at Hoosic and a few other places, were placed in the 

 Hudson river series, notwithstanding they lie far towards the Hoosic mountain range. 

 With this disposition I was never satisfied ; but so strong was the determination, at the 

 time I published my report, to consider all these slates and shales as metamorphic beds 

 belonging to the New-York system, that I did not make up my mind to break away from 

 the doctrine. I taught the same doctrine, too, in the spring of 1838, to my class in natu- 

 ral history in Williams College ; but I was led the next year to abandon it, from the great 

 difficulty of maintaining it against the light of some facts which had fallen under my 

 observation. 



In my first examinations of the slates of this region, I committed a serious error, in 

 taking it for granted that all the beds near Troy belonged truly to the Hudson river shales. 

 Accordingly I made that place my starting point, and examined carefully all the exposed 

 rocks to the eastward, for the purpose of ascertaining the line of demarkation, if any existed, 

 between these and the eastern slates. The error consisted in the first assumption ; instead 

 of which, the rocks near Troy, and lying adjacent to the great travelled road to the east, 

 are composed chiefly of Taconic slate. The belt of the Hudson river series resting upon 

 the Taconic slates, and extending north from near Chatham four-corners in Columbia 

 county, terminates south of the road, which takes a circuitous route beyond the northern 

 prolongation of the belt. Hence the reason why no change was observed ; and hence, 

 following a wrong direction, the beds of roofing slate were enabled to maintain themselves 

 in a wrong position. My object is here to correct the error, into which I had fallen in 

 spite of a feeble consciousness that I was all the time wrong. 



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