GEOLOGT. 37 



from the same place into every seaport from New Or- 

 leans to Eastport. It is used for the underpinning of 

 houses, door steps, hearths, jambs, &c, &c. 



Graywacke, in some of its deposits, resembles sand- 

 stone. But besides embracing recks composed of 

 grains, it extends to those consisting of large pebbles, 

 sometimes a foot in diameter, and frequently so loosely 

 cemented, as to fall to pieces from the effects of the 

 weather, and other gradual operations of time. 



An extensive and most singular deposit of graywacke 

 is found nearly the whole distance from Boston to Provi- 

 dence. A circumstance respecting this deposit of 

 graywacke coincides with that in another on the heights 

 of Catskill mountains. The circumstance is, that the 

 highest points of elevation in both cases, consist of the 

 coarsest pebbles. In the descent, both rocks become 

 finer and more compact in their texture, until they 

 finally pass into slate. 



Another most singular and unaccountable fact, which 

 is particularly striking in the New England deposit is, 

 that ledges are intersected by numerous seams, which 

 cut, not only the largest pebbles, but the finest grains, 

 leaving a surface almost as smooth as if it were polished. 

 This fact may be witnessed in the numerous walls built 

 of this material in Dorchester and Roxbury, which by 

 the aid of these seams present an even surface in front, 

 notwithstanding the general fracture of the rock is un- 

 commonly ragged and uneven. 



The fact is stated merely, any may explain it who 

 are able. 



Some of the finest slates, and even the material of 

 which hones are composed, are classed by geologists 

 under the stratum of graywacke. 



Argillite, or common slate, used in schools and for 

 the roofs of houses, is an abundant rock, but less com- 

 mon than most of those already described. Extensive 

 ranges of it exist in Vermont, which furnished during 

 the last war, large quantities of a good quality for the 

 roofs of houses. But as it is less expensive transporting 

 it across the Atlantic, than down the Connecticut, the 



VOL. i. NO. ii. 4 



