20 Mesozoic and Cmnozoic Geology and Paloiontology. 



kind of trap, very abundant in Nova Scotia, is Tufa or Tuff, or vol- 

 canic sandstone, a rock of earthy or sandy appearance, and of gray, 

 greenish or brown color. It consists of fine volcanic dust, and scoriae, 

 popularly known as the ashes and cinders of volcanoes, cemented to- 

 gether into a somewhat tough rock. Modern tufa, quite analogous to 

 that of tke trap, is ver}^ abundant in volcanic countries, and some- 

 times sufficiently hard to be quarried as a stone. 



In the valley of the Salmon river, 4|^ miles eastward of the village of 

 Truro, the eastern extremity of the New Red Sandstone is seen to rest 

 unconformably on hard, reddish, brown sandstones and shales, beloug- 

 ino- to the lower part of the Carboniferous system, and dipping N. 80 

 deo-rees, E. at an angle of 40 degrees.' At this place the overlying forma- 

 tion is nearl}^ horizontal, and consists of soft and rather coarse, bright, 

 red, silicious sandstones. Southward of Truro, at the distance of less 

 than a mile, the horizontal soft red sandstone is seen in the banks of a 

 brook, to run against hard, brownish grits and shales, dipping to the 

 eastward at angles varying from 45 to 50 degrees. Westward of this 

 place, the red sandstones extend in a narrow band, about a mile in 

 width, to the mouth of the Shubenacadie, ten miles distant. This band 

 is bounded on the North by Cobequid Bay, and on the South by high- 

 Iv inclined sandstone, shale, and limestone of the Lower Carboniferous 

 series. In the coast section, between Truro and the Shubenacadie, the 

 red sandstone presents the same characters as at the former place, ex- 

 cept that near the Shubenacadie, some of the beds, which, like most of 

 the red sandstones of Truro, have a calcareous cement, show a tenden- 

 cy to arrangement in large concretionary balls. West of the mouth of 

 the Shubenacadie, the red sandstone ceases to form a continuous belt, 

 but occurs in several patches, especially at Salter's head, Barncote and 

 Walton. At the latter place, it is seen to rest on the edges of sandstones 

 and other rocks of the Lower Carboniferous system, affording a very 

 fi.ne example of that unconformable superposition, which, in (Geology, 

 proves the underlying formation to have been elevated and disturbed 

 before the overlying beds were deposited upon it. 



Westward of Walton, the estuary of the Avon river and Minas basin 

 make a very wide gap in the new red sandstone. On the western side 

 of Minas basin, however, this formation attains its greatest width and 

 grandest proportions. Blomidon is the eastern extremity of a long 

 band of trappean rocks, forming an elevated ridge, named in the greater 

 part of its length the " North Mountains." This ridge is about 123 

 miles in length, including two insular portions at its western extre- 

 mity, and does not exceed five miles in breadth, except near Cape 



