EASTERN MASSACHUSETTS. 



399 



The felsparoid was divided as follows : Common, Quartzose, Epido- 

 tic, and Granitic Folsparoid. 



Tho felsitc ho classes under tlic head of Petrosilcx, but thinks that, 

 instead of petrosilex being a simple mineral, as it was then generally , 

 regarded, possibly it might be compound in its nature. 



He makes the following divisions of the petrosilex : 



r Flinty Petrosilex. 

 " Simple Petrosilex i Sonorous " 



Jasper " 



_Novacular " 

 " Porphyritic Petrosilex." 



The name simide petrosilex seems to have been confined to the more 

 apparently homogeneous folsites, while tho term porphyritic p)ctro&ilex 

 was given to those rocks supposed to have a base of simple petrosilex, 

 or of fclsparoid which held enclosed porphyritic crystals. The simple 

 petrosilex was thought to pass into wacke and fclsparoid. 



Tlie common argillite of the country was denominated argllloid, and 

 it was supposed to pass into petrosilcx. He separated it into the fol- 

 lowing divisions : Common and Novacular Argilloid: An imperfect 

 chemical analysis was made of some of the argilloid tliat resembled the 

 sonorous petrosilex. 



The conglomerate of the district was called ivaclce, !J.r, Godon says 

 of it : — 



*' How much attention soever I have paid to the examination of this rock in 

 <iitu, I have never observed in it any distinct stratification. It commonly 

 unites with the rocks previously described, and with amygdaloid, often by an 

 insensible transition. I possess specimens, which, on pieces of four inches 

 square each, present its different passages to fclsparoid, aniphiboloid, simple 

 and porphyritic petrosilex, argilloid, &c." 



His explanation of its origin is interesting, not only as illustrating 

 some of the views of that time, "but also from its general resemblance to 

 the conclusions and statements in some more recent articles on the geol- 

 ogy of Eastern Massachusetts. 



" If perniittcd to venture an opim'on on the mode of its formation, Ave may 

 suppose, that, as we fuid in it specimens of almost all the rocks, which pre- 

 dominate in the country, it originated from a motion, which disturbed and 

 divided the vast deposits of felspathic, porphyritic, petrosiliceous, &c. rocks, 

 while they were passing from the state of Ihiidity to that of solidity. This 

 motion ought to be supposed as having taken place before tlie complete solidi- 

 fication of these rocks ; since the compactness of the wacke indicates that its 





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