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SKETCH OF THE 



I propose including all the rocks which occur in this district under 

 the following heads, viz : 



Granitic rocks, 

 Gneiss, 

 Quartz rocks. 



Micaceous schist, 

 Chlorite ditto, 

 Talcose ditto. 



Argillaceous, 

 Hornblende rocks, 

 Greenstone, 



Serpentine, Marble, and Porphyry. 



Under the head granitic rocks shall be included those only which 

 have not a slaty structure, and which are composed of tivo or more of the 

 following ingredients ; viz. quartz, mica, felspar, cleavlandite, hornblende, 

 and occasionally steatite, talc, and chlorite. The only exception to this 

 rule will be found in some varieties of rocks, in which hornblende^ pre- 

 ponderates, and which shall be placed under the head " hornblende 

 rocks." 



Stratified, as well as imstratified, rocks, shall be included with the 

 granites, as every one who has visited this district must allow that distinct 

 and well-marked granite does occur in strata ; and I am compelled to 

 state this in opposition to the high authorities of Macculloch and 

 Phillips. Mr. Phillips allows (see Outlines of Geology, p. 164,) that 

 granite is sometimes found disposed " in beds which possess the ordinary 

 characters of stratification,'' and Dr. Macculloch, in support of his 

 opinion, (see Journal of Sciences and Arts) is obliged to account for 

 the adduced instances of stratification in this rock, by declaring that 

 " they may all be referred to laminar concretionary structure on the 

 large scale," — or that the instances alluded to are " portions of gneiss of 

 which the structure so often becomes perfectly granitic,'' or lastly, that 

 they are " veins of granite traversing the gneiss in directions parallel to 



