54 REPORT OF THE 



again beneath the carboniferous basin of Ohio, on the one hand, 

 and of Indiana on the other. At Cincinnati is another swell, 

 from the summit of which the overlying formations have been 

 denuded, and here the Hudson River Group again appears. Like 

 most of the other groups of the Palaeozoic System, it has through- 

 out the northern and north western States, a very great geo- 

 graphical development 



II. UPPER SILURIAN SYSTEM. 



5. — Clinton Group. 



At the eastern extremity of Drummond's Island, the lower 32 

 feet of Dickinson's quarry constitute the upper portion of the 

 Clinton Group of New York. It is an argillo-calcareous lime- 

 stone, fine grained and very evenly bedded, in layers from two 

 to three feet thick, having a very gradual dip toward the south. 

 In color it is nearly white, some layers having an ashen hue. 

 The rock presents to the eye every appearance of a most beau- 

 tiful and desirable building stone, remarkably easy of access 

 and eligibly situated for quarrying. In November, 1859, the 

 company organized for working the quarry got out a large 

 quantity of fine blocks for building purposes. Severely cold 

 weather arrested their operations, and on the return of Spring, 

 the fine blocks quarried out were found considerably shattered, 

 apparently by the action of the frost. This effect was undoubt- 

 edly due to the sudden freezing of the stone while yet contain- 

 ing a large amount of quarry water. Whether a rock containing 

 so large a per centage of argillaceous matter would not, under 

 any circumstances, prove too absorbent and retentive of moist- 

 ure, to stand in exposed situations in our severe climate, 

 remains yet to be ascertained; but I have some hope, that if 

 quarried in early summer, and left to dry before the approach 

 of frost, it might be found durable. 



As a lithographic stone, whatever its qualities for building 

 purposes, I believe some of the layers will answer well, when 

 polished ; the surface, to the naked eye, is quite free from imper- 

 fections, and under a glass some portions are so homogeneous 



