I 



GEOLOGY OF EAST BOSTON. 449 



Boston where I am living (East Boston) is 

 built on an island, one kilometer and a half 

 long, extending from north to southeast, and 

 varying in width at different points from two 

 to six or seven hundred metres. Its height 

 above the sea-level is about sixty feet. This 

 little island is composed entirely of glacial 

 muddy deposit, containing scratched pebbles 

 mixed with larger boulders or blocks, and 

 covered also with a considerable number of 

 boulders of divers forms and dimensions. At 

 East Boston you cannot see what underlies 

 this deposit; but no doubt it rests upon a 

 rounded mass of granite, polished and grooved 

 like several others in Boston harbor. The 

 house I occupy is on the southern slope of the 

 island, and they are now digging more to the 

 north, a new street parallel with one which 

 runs along the shore. On the cuts of this ex- 

 cavation, at a depth of twelve feet below the 

 surface, a bed of Zostera marina may be seen 

 which crosses the whole hill almost horizon- 

 tally, with a slight inclination to the northeast, 

 thus forming a regular and continuous bank 

 in the very middle of the drift. This bed of 

 zostera, which, thanks to the excavations now 

 making, I have been able to trace over an 



extent of several hundred metres in all direc- 

 voL. n. 4 



