BOTANY, CONCHOLOGY, AND GEOLOGY. 49 



city of Worcester, and another line from Sancoty to 

 Boston, letting the former line terminate at Worcester 

 and the latter at Boston, he will not be very far out of 

 the way in concluding that the materials making up 

 the body of our island came from somewhere between 

 those lines, nearer or farther. It would be an exceed- 

 ingly interesting investigation if some one — say the 

 principal of the High School or of the Coffin School, 

 or at any rate some one geologically inclined — would 

 put a few specimens of small bowlders, gathered from 

 different parts of the island, into his satchel some vaca- 

 tion, and compare them with ledges in Bristol and 

 Plymouth Counties, with a view to seeing whence the 

 ragged material was probably torn. Bowlders in the 

 eastern part of Long Island have been traced to ledges 

 in Connecticut, and bowlders in Brooklyn have been 

 distinctly traced to the Palisades of the Hudson. 

 Usually the transportation of drift stuff in New Eng- 

 land was not over a distance of ten or fifteen miles; 

 and it is possible that the matrix out of which the 

 Nantucket material came lies to-day sunken at the 

 north of the island, in Nantucket Sound. But as " till," 

 or drift stuff, is known to have been carried in New 

 England nearly a hundred miles, it is possible that 

 Nantucket may have come from what is now Bristol or 

 Plymouth County, or from as far north even as Nor- 

 folk County. 



But first, as to the period when that which is 

 called Nantucket came into existence. It is knowm by 

 the merest school-boy to-day, that there have been 

 in the history of this globe three great geological eras, 

 called the primary, the secondary, and the tertiary; and 

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