90 



ROCKS ABOVE THE TACONIC SERIES. 



Another instance of complication occurs in the adjacent hill northeast of Bald mountain. 

 Fig. 12 is a section illustrative of its structure. 



\fe^ 



a. Calciferous sandstone : towards c , on the west, it dips moderately to the east ; but ascending the ridge, the dip 

 increases, and finally at a, the summit, it is reversed, or to the west; but here it comes in immediate contact 

 with the coarse taconic slate, *, dipping steeply to the east. Well characterized taconic slate crops out on the 

 rosters slope, just above the main road, covered partially by debris. 



I have introduced this illustration for the purpose of clearing up some difficulties which 

 might arise hereafter in the examination of this or the neighhoring hills, where the cal- 

 ciferous sandstone apparently plunges heneath the taconic slate, when viewed in certain 

 positions only; for if only the western slope should be compared with the eastern, without 

 a careful examination of the summit of the ridge, a very false view would be taken of the 

 position of the rocks forming this hill. 



IV. THE TACONIC SYSTEM IN RHODE-ISLAND 



Position of the Smithfitld limestone : it is the Stockbridge limestone. Other members of the Taconic system. 

 Only a fragment of this system remains, it haring been probably destroyed by denuding agents. Debris 

 found in the sou", and in the rocks composing the Cumberland coal basin. 



In July of the present year (1844) , I was induced to visit the State of Rhode-Island, 

 principally for the purpose of examining the Smithfield limestone, a rock which for a long 

 time has been known in the market as furnishing an excellent lime. I had often made 

 the enquiry whether this rock is an equivalent of the Primary limestone of St. Lawrence 

 and Essex counties; or whether it is of the age of the Stockbridge limestone, the marble 

 of the Taconic system. The satisfactory solution of this question, I deemed of sufficient 

 importance for a journey to the place ; inasmuch as no one, so far as I had access to 

 printed publications, had expressed themselves very clearly on those points in which I 

 • the mosl interested. 



The Smithfield limestone lies in the valley of the Blackstone river, about ten miles 

 north of Providence. It occupies but a small area, and lies in the midst of the primary 



