310 HUDSON RIVER GKOUP. 



ringing slates. There are many different shades of color in the clay slate, south of 

 Bridport. 



When this slate takes carbonate of lime into its composition without altering its black 

 color, though at times the argillaceous odor has disappeared, we call it calcareous slate. 

 In the greater part of the range this variety abounds, especially between Canada line and 

 Bridport. Every grade, from pure clay slate to slaty limestone, is found. It is not im- 

 probable that the source of the dove-colored and silicious limestones in some places may 

 be found in the melting up, as it were, of this calcareous rock. This struck us particu- 

 larly at Snake Mt., where, within the distance of a mile, a great thickness of limestone 

 destitute of stratification succeeds this calcareous slate, along the line of strike. 



Prof. Thompson gives the following account of this variety in Chittenden County: 

 " The black slate is generally contorted and crushed, and abounds in seams of white 

 calcite, varying from a line to a foot in thickness. Still there are places where the spar 

 has not been injected, and where the lamination has been disturbed. Cases of this kind 

 may be seen on the east side of Pottier's Point, and at Appletree Point. But all this 

 slate doubtless contains too much lime, and is too brittle to be used for any better purpose 

 than making roads. This slate in many places, particularly where it is fragmentary, has 

 its surface covered with a black glazing, giving it very much the appearance of anthracite. 

 This may be seen near the meeting house in Charlotte, and at Lonerock Point, and it has 

 led some to suppose that coal might be found in connection with it. But I believe very 

 little, if any, money has been thrown away, in the vain search for coal in this county." 



This variety is well developed at the northwest end of Snake Mountain, in Addison. 

 We ascended the mountain in the bed of a small stream, which has exposed the slate 

 almost every foot of the way. We found no seams that were not calcareous, and the 

 amount of lime generally is quite large. This is an exposure that Prof. Emmons has 

 examined with care. He regarded the slate as the uppermost member of the Taconic 

 system, calling it the black slate. Our views upon this subject are given in full elsewhere. 



Often at this exposure thin beds of black limestone alternate with the slate, as in the 

 Utica slate. This is common throughout the whole range. At Charlotte, at the foot of 

 Glebe Hill, they are unusually numerous. At Stave Point in Colchester they have been 

 burnt for quicklime, and answer very well for that purpose. 



At St. Albans Point in clay slate, and upon Ram Island in St. Albans Bay, there are 

 beds of silicious slate. This is a mass of flint or quartz rock of the same color as the 

 slate. It is called black jasper by those that live in the vicinity, and this name gives a 

 very good idea of its appearance. Upon Ram Island, parts of it are brecciated. We 

 have traced this bed for about three miles, in a north and south direction. 



It is unusual to find beds of sandstone interstratificd with the shales and slates of this 

 group, except in Rutland County. This sandstone is free from lime, and is durable and 

 compact, like the sandstone of the red sandrock series that is found in the vicinity. 

 The principal locality of it is in the northwest part of Benson, in a slate quarry. At the 

 west end of the quarry there is a bed of sandstone six inches thick ; at the east end there 

 is another, fifteen feet 'thick (No. r g & ). These beds are probably numerous in this region, 

 lying about three-quarters of a mile west of the hill of red sandrock. We should expect 

 to find small beds of sandstone in the vicinity of that rock. 



