150 FIELD MEETING AT MARBLEHEAD NECK. 



upon by the President, and spoke of the geological fea- 

 tures of the Neck. He said that porphyry, syenite and 

 greenstone were the principal formations, and, while por- 

 phyry was very abundant on the Neck, there were no 

 specimens of it found in Marblehead proper. Some of 

 the ledges showed very fine and handsome specimens 

 of banded porphyry. Mr. Gregory spoke in a general 

 way of the geology of the county and of the state, and 

 said that there should be a full and complete collection 

 of rocks and minerals of the state for preservation in 

 the county, and suggested that the Institute would do 

 well to take the initiative. It would be both valuable 

 and interesting. 



Along the shores of the Neck are found great quantities 

 of porphyry chippings, so called ; these were, without 

 doubt, left by the Indians, who formerly roamed over 

 the vicinity, and who made their cutting implements from 

 porphyry, which is very hard; these Indians probably 

 came to the ledges and chipped stone into the general 

 shape of arrowheads, or other weapons, and carried them 

 away to be finished at leisure. The speaker said that 

 large quantities of these chippings could be found in 

 various places along the shore. Mr. Gregory referred 

 to the beautiful porphyry tables at the centennial exhibi- 

 tion in Philadelphia, which were highly polished, showing 

 a remarkable finish and lustre. He had made experiments 

 with the stone found here, but had been unable to produce 

 the desired effect. 



Mr. Gregory also alluded to the plants spoken of by 

 Mr. Sears, saying he had been much troubled by the 

 horsemint on his farms at Middleton. 



Prof. Edward S. Morse was the next speaker. He 

 referred to the plants and marine animals noticed during 



