898 



THE AZOIC SYSTEM AND ITS SUBDIVISIONS. 



ports of the State Geologist, published while the work was going on. 

 The scheme here presented is as complete as it has been found pos- 

 sible to make it. So numerous are the contradictions in the published 

 statements made from year to year, that only an intimate personal 

 acquaintance with the geology of New Hampshire would make it possible 

 to prepare a connected scheme of the subdivisions of the geological 

 formations of that State, as from time to time set forth in Professor 

 Hitchcock's reports. 



EASTERN MASSACHUSETTS. 



The first paper of which the writers are aware, relating to the lithol- 

 ogy of the vicinity of Boston, is that of Mr. S. Godon, entitled, *' Minera- 

 logical Observations, made in the Environs of Boston, in the Years 1807 

 and 1808." (Mem. Am. Acad., 1809, (1) IIT., pp. 127-154, with a 

 Table; Ann. Mus. Hist. Nat, 1810, XV., pp. 455-472.) From this 

 paper it appears that Mr. Godon united under the name amyhiholold 

 all the roeks in this region which he supposed to be composed of am- 

 phibole and feldspar, when the former mineral predominated. When 

 the latter was more abundant than the hornblende^ the rock was called 

 felsparoid. It seems from his descriptions that he included under the 

 term araphiboloid part of the granitic and all of the basaltic rocks 

 (diabase, diorite, and melaphyr) except the amygdaloid and possibly 



some diabase. 



The amphiboloid was divided into the following series : Common, 



Granitic, Trappine, Porphyritic, Epidotic, Quartzose, Micaceous, and 

 Talcous Amphiboloid. The presence of epidotc in small veins both in 

 the amphiboloid and felsparoid was noticed and described. 



The felsparoid included the hornblendic granite both north and 

 south of Boston, and probably some of the coarser diabases. The fel- 

 sparoid was said to be often micaceous, and in general to present no 

 distinct stratification. Mr. Godon also remarks, that *Hhe transition 

 of felsparoid to petrosilex and porphyritic petrosilex is frequently ob- 

 served in the compass of the present observations." He cites, as local- 

 ities where the transition can be observed, Milton, Blue Hills, and 

 Maiden. 



