OF THE TACONIC SYSTEM. 
107 
§ 2. Marbles. 
The Stockbridge limestone furnishes by far the greatest amount of the native marbles 
used in the United States. 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 Tro}^, 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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