205 



cordial welcome with wliich tiicir friends of tlie town re- 

 ceived them, 



Mr. Barden would act on his friend's suggestion so far 

 as to give a slight delineation of the geology of this region. 

 It was, in fact, a pleasure to speak thus to a company from 

 such various localities, most of whom, probably, never visit- 

 ed these quarries before. This is a region of hard, stern 

 granite ; unpoetical, perhaps, but full of interest to the 

 mineralogist. The rock seems like sienite, from the very 

 dark hue of the mica, but is yet a true granite witli all tho 

 value of that eldest of all the rocks. Within some thirty 

 years three veins have been found in it, where- the compo- 

 nents have crystalized more separately, and in larger masses 

 than common ; and here a variety of rare minerals had been 

 gradually detected. Among these the showiest and best 

 known was the Green Feldspar. Black Mica was found in 

 good specimens, and Quartz of very fanciful colors and fine 

 forms. 



Mr. Francis Alger of Boston, pursued the subject with 

 some description of another mineral detected to-day, which 

 had occasioned some discussion. Some had thought it 

 lolite, but he rather supposed it to be Fluor Spar. He had 

 been especially interested in examining the trap dykes that 

 cut through the primary rock, and the alterations in that 

 rock, induced by the intrusion of these once molten masses. 

 The Green Feldspar of this place he thought quite equal 

 to that from Siberia. 



James J. H. Gregory of Marblehead said that some cu- 

 rious facts as to the crystallization of this granite might be 

 detected in the structure of the rock as it is to-day. Masses 

 of other kinds than granite were inclosed in it, themselves 



