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course of study miglit be made upon this rock alone. The 

 State Map does not notice the porphyry of this vicinity, or 

 only feebly indicates it. This is certainly a grave defect, 

 and ought to be amended ; for the rock is too raie and 

 striking in its charactcj-s to be overlooked in such a work. 

 Greenstone is found not far from here, but it is somewhat 

 different from that of Marblehead, being of a rather slaty 

 character. 



Mr. Tracy, of this place, has thrown out the suggestion 

 that the type of vegetation in a given territory is directly af- 

 fected by the nature of the rock formations there (ound. Ho 

 had no doubt but this idea was based on fact. He had to- 

 day made a short excursion of a mile and a half, or so, to 

 look at some of the curious exhibitions of drift to be seen 

 among these hills. In this ramble he had seen for hims'elf 

 that a difference could be detected in the forest growth along 

 either side of the line of junction between the porphyry and 

 the granite. No doubt a closer study would set this matter 

 in a clearer light ; it is certainly a point deserving of care- 

 ful attention. He. had been to-day among bowlders of every 

 size, from small pebbles to a small house, for some of them 

 were at least one hundred and twenty feet in circumference 

 and thirty feet high. And yet these great blocks are not 

 left with sharp angles, but in almost all cases are rounded and 

 finished off like beach-stones. Undoubtedly they have all 

 been moved, and belong to the great mass of the drift forma- 

 tion. In the deep woods near the South Danvers line, he 

 had been piloted by Mr. Tracy to find what he could never 

 could have found alone — the somewhat noted and very re- 

 markable " Phaston Rock.'" A more curiously situated 

 rock would be hard to find, or to conceive of. A vast block 

 shaped like half a pear with the flat side undermost, some 

 ten or fifteen feet in greatest length, lies precisely balanced, 

 and firmly sustained on four small rounded stones twelve or 

 fifteen inclies in diameter, just onthebrhik of a precipice, 

 over whicli its smaller end projcpts for almost lialf the length 



