Shale. 



213 



ing divided into rhomboidal masses, by one or two sets of parallel 

 seams. On the north bank of Westfield river, in West Springfield, 

 this division is remarkably distinct, and the surface of the rock pre- 

 sents an interesting chequered aspect. The same is the case in the 

 northeast part of Greenfield, just below Turner's Falls. 



3. Shales. (Nos. 199 to 204.) Under this term I include all 

 the varieties of argillaceous slate, sometimes called slate clay, found 

 in connection with the secondary rocks. And in Massachusetts such 

 slate occurs only as a member of the new red sandstone series : of 

 that formation it constitutes a very important part. Its colors are 

 gray, red, and black ; and in hardness it varies from that of tender 

 schistose marls, to a degree of induration approaching that of sili- 

 ceous slate. The red variety is most abundant ; especially in the 

 region of Enfield and Hartford, in Connecticut. Sometimes it takes 

 mica and sand into its composition, and then passes into the red mi- 

 caceous sandstone, as already remarked. When black, it is gener- 

 ally bituminous, as at Sunderland, and at Middletown, Connecticut ; 

 where are found upon it the impressions of fish and vegetables. 

 Some of the black colored slate, as at Turner's Falls, splits into ir- 

 regular, somewhat wedge-shaped pieces ; and indeed, easily disinte- 

 grates and falls to pieces ; when it resembles comminuted coal. It 

 frequently contains sulphuret of iron ; which, by decomposition, 

 causes the slate to exfoliate : in some places, also, as at Turner's 

 Falls, and on Chicopee and Westfield rivers, this shale abounds in 

 nodules of argillaceous iron ore, of a poor quality. Some of the 

 black non-bituminous shale of this formation, has almost lost its 

 slaty structure in the process of induration. Thin pieces of it give a 

 ringing sound when struck. This variety abounds in the vicinity of 

 Turner's Falls ; as, indeed, nearly every other variety does. There 

 we find a gray variety, which is so soft that it may be impressed by 

 the finger nail. 



If it were possible to doubt that the new red sandstone formation 

 was deposited from water, the surface of some of the layers of this 

 shale would settle the question demonstrably. For it exhibits pre- 

 cisely those gentle undulations, which the loamy bottom of every 

 river with a moderate current, presents. (No. 198.) But such a 

 surface could never have been formed while the layers had that high 

 inclination to the horizon, which many of them now present : so that 

 we have here, also, decisive evidence that they have been elevated 

 subsequent to their deposition. 



