214 Scientific Geology. 



On Westfield river in West Springfield, both the red and black 

 shales are traversed by numerous veins of satin spar ; itself often 

 of a redish hue. They are rarely more than an inch wide, but often 

 several feet long ; and run uniformly across the laminae of the slate. 



In the same place the black shale, as well as the bituminous marl- 

 ite, and some varieties of slaty sandstone, contain masses of septaria, 

 or the Ludus Helmontii. They vary in size from an inch to 5 or 6 

 inches in diameter, and are usually flattened or reniform. The en- 

 velope appears to be argillo-ferruginous as well as calcareous ; and 

 the cavities are lined, and sometimes filled, by white calcareous spar. 

 The interior is divided into irregular masses, or sometimes into poly- 

 gonal prisms. 



The hypothesis which imputes the cavernous structure of these 

 argillo-calcareous masses to dessication, and their subsequent filling 

 up to the infiltration of carbonate of lime in a state of solution, seems 

 to me liable to few objections ; and, indeed, is quite satisfactory. But 

 I have already given it somewhat in detail, when speaking of colum 

 nar argillaceous iron ore. 



4. Limestones. (Nos. 205 to 216.) When the black bituminous 

 shale, that has been described, takes into its composition enough 

 of calcareous matter to produce effervesence with acids, it. becomes 

 bituminous marlite. It is not very common in this sandstone forma- 

 tion. Yet one finds it in considerable quantity on the banks of West- 

 field river, in West Springfield ; and I have ascertained that the 

 stratum of slate in Sunderland, which contains the best preserved 

 relics of fish, is bitumious marlite. Although this rock contains but 

 a small proportion of calcareous matter, yet it certainly does not 

 deserve to be described as a distinct rock ; and it may be conven- 

 iently mentioned under the head of limestones. 



Strongly fetid limestone occurs, interstratified with the micaceous 

 sandstones of this formation, at two places in the northwest part of 

 West Springfield. At the most northern locality, I noticed only a 

 single bed about 10 feet thick : but two miles south from that spot, 

 several beds, not far apart, may be seen, associated with greenstone 

 as well as sandstone. The rock at both places is of a dark gray 

 color and nearly compact. Its fetid odor when struck, is exceed- 

 ingly strong, so as even to produce nausea. It is wrought to some 

 extent for water proof cement, and it answers well. (Nos. 213 to 215.) 



I doubt whether much genuine bituminous limestone exists in the 

 /iew red sandstone in Massachusetts. Yet when the bituminous 



