274 



Scientific Geology. 



ularities of the slate. The dark strip is a bed of anthracite a few 

 inches thick ; and the dotted part shows where the diluvium has slid- 

 den down upon the rock. The slate is so highly impregnated with 

 carbon as to be quite dark colored, and might perhaps be denomin- 

 ated shale. Near the anthracite bed it abounds in vegetable remains. 

 I could discover no strata seams distinct from those that separate the 

 layers of slate ; and it is very doubtful whether this rock ought to be 

 regarded as stratified at that place. 



Coast Section in Graywacke Slate : Newport R. I. 



It is obvious that this slate must have been bent into its present 

 form while yet in a plastic state ; although its elevation to a nearly 

 perpendicular position, might have been 'the result of a subsequent 

 convulsion. It will be recollected, that in giving a history of our 

 tertiary strata, I have exhibited some remarkable examples of tortu- 

 osity in the clay beds, which bear a strong resemblance to the one 

 figured above ; and perhaps both were produced in a similar manner, 

 however difficult it may be to assign any adequate cause. Other sim- 

 ilar cases I shall describe when I come to speak of mica slate and 

 gneiss. 



In another place on the same coast, near where the preceding 

 sketch was taken, the graywacke slate seems to have assumed the 

 form of a paraboloid, or an ellipsoid, whose longer axis coincides 

 nearly with the meridian. The upper part of this paraboloid having 

 been worn away, leaves the basset edges of the slate as exhibited 

 below. 



The dotted portion in the following sketch, is covered by debris and 

 sand ; but very probably the position of the laminae is as represented. 

 The dip of the slate is outward on every side ; or in such a direction 

 as it would be, if the layers curved around a paraboloid, or ellipsoid, 

 from which a segment had been cut off 



