ON NEW ENGLAND EARTHQUAKES. 



25 



State. He had never seen a volcano, but the curiously radiating ridges, and semi-circular 

 mounds and depressions, suggested a common origin, and that volcanic. 



Our geologists are now prosecuting their examinations into the physical geology of New 

 England, in a way unknown when most of the State reports were published ; and, although 

 the purpose with which this paper was commenced has been necessarily abandoned for the 

 present, yet these most interesting locaUties may be examined by those now in the field, 

 and useful results expected. 



The regions indicated by the earthquakes catalogued, are as follows : — 



1. A region in Canada, somewhat elliptical in form, with the city of Montreal at its 

 ■western focus. 



2. A region around the mouth of the Merrimack River, in New Hampshire and Massa- 

 chusetts, and extending to Boston. 



3. A region smaller than either of the others, around Ncav Haven, Lyme and East 

 Haddam. 



These are, as will be seen, comparatively independent, although a severe shock may be 

 simultaneous in all. The trap indications (and the word trap is here used in its popular 

 signification, to mean any felsp;ithic, igneous rocks, containing much augite and horn- 

 blende,) are more continuous, and are also widely diffused. Northern Vermont, the Con- 

 necticut valley, central Connecticut, and eastern Massachusetts, are in some sort distinct, 

 although not differing so much as to be referred to different ages ; for it seems probable 

 that the dikes have been formed at intervals in the same locality, and their formation may 

 be, and doubtless is, now going on from time to time, at various depths below the surface, 

 and by the high temperature they bring in contact with the cold rock, through which 

 they break, or into whose cavities they run, produce the tremors and disturbances we call 

 earthquakes. 



TABULAR VIEW OF NEW ENGLAND EARTHQUAKES. 



limiOIUS BOST. SOC. NAT. UlST. VOL. H. 



