25 



curring in Lynn, Saugus, Marbleliead, and Newbury ; and says 

 in this connection, " These rocks are, throughout this region, dis- 

 tinctly stratified, and are closely associated with dioritic, chlo- 

 ritic, and epidotic strata. They appear to belong, like these, 

 to the great Huronian system." Dr. Hunt has included here all 

 the rocks which it is proposed to refer, in this paper, to the 

 Huronian series, save the binary and hornblendic granites 

 (which are so characteristic of Eastern Massachusetts) and the 

 limestones. In consequence of finding the Eozoon canadense 

 in the serpentinic limestone of Newbury, Dr. Hunt, in 1870,^ 

 referred this limestone and the associated rocks, as well as the 

 more crystalline and less serpentinic limestones of Chelmsford 

 and Bolton, and the gneiss in which they are included, to the 

 Laurentian system. He made no mention, in this connection, of 

 the serpentinic limestone in Lynnfield, which is probably of the 

 same age as the Newbury deposit, since the associated rocks 

 appear to be the same. Prof. C. H. Hitchcock, also, in 1871,^ 

 referred to the Triassic period, certain diorites in the vicinity of 

 Salem and Boston, which are here referred in part to the Nau- 

 gus Head series, and in part regarded as of Huronian age. 

 And more recently, in his late report (1875) on the geology of 

 New Hampshire, he has applied the term "Labrador" to this 

 broad Huronian area, although these rocks have scarcely a 

 single character in common with the Labrador or Norian series 

 as defined by Dr. T. Sterry Hunt and the Canadian Geological 

 Survey.^ It will be shown in the sequel, however, that all the 

 rocks within the area described probably belong to one and the 

 same lithological and stratigraphical series, the general characters 

 of which stamp it as Huronian. 



A glance at the maps will show that the attempt to delineate 

 this formation lithologically, ^. e., to show the distribution of 

 its various lithological members, has been attended by moderate 



^ Amer. Jour. Sci. (2), xlix., 75. 



2 Geological Map in Walling's Atlas. 



3 Still later, in the atlas of the New Hampshire Survey (1878), Prof. Hitchcock 

 recognizes the existence of several limited Hiironian areas in Essex County. 



