1875.] 509 [Hunt. 



abundant along the eastern coast of Massachusetts, Maine and New 

 Brunswick, and which passes on the one hand into a jaspery petro- 

 silex, and on the other, into a finely granular, almost granitoid rock. 

 In its typical and most common form, it is a fine-grained impalpable 

 mixture of orthoclase and quartz, generally colored some shade of 

 red, brown, or purple, and porphyritic from the presence of feldspar 

 crystals, chiefly orthoclase, often with grains of crystalline quartz. 

 The porphyries of Lynn, Marblehead and Salem, and the so-called 

 jaspers of Saugus and Newbury, belong to it. This rock is identical 

 with the porphyry which accompanies the crystalline iron ores of 

 southeastern Missouri, and is also well displayed on the north shore 

 of Lake Superior. It is, in all of these localities, distinctly stratified, 

 and has been by the speaker referred to the Huronian series of rocks. 

 [See the Proceedings of this Society for October, 1870, pp. 45, 46, 

 and also the late descriptions of Pumpelly and Schmidt, in the geo- 

 logical report of Missouri for 1873.] This porphyry, in the form of 

 pebbles, often forms conglomerate beds in the Keweenaw or copper- 

 bearing series of Lake Superior, as is well seen in the Calumet and 

 Hecla, and the Boston and Albany mines. 



As regards the relations of the eruptive granites of our Eastern 

 coast to the Braintree fossiliferous slates, Dr. Hunt remarked that 

 granites on Marblehead Neck, which resemble those of Cape Ann, are 

 seen to cut the still older porphyries, as he had pointed out in the 

 Proceedings of the Society, cited above. 



In reply to another question, Dr. Hunt said that the relation of 

 the similar fossiliferous slates in the vicinity of St. John, N. B., to 

 the Huronian or Green Mountain' series, was very apparent. The 

 unchanged fossiliferous strata are seen to rest on the crystalline 

 Huronian strata, and include, in some cases, fragments derived from 

 these. He also remarked that in this region there is a series of 

 granular limestones interstratified with micaceous quartzites, which 

 pass into micaceous gneisses, containing veins of endogenous granite. 

 These strata, which are like some portions of what he has called the 

 White Mountain, or Montalban series, are likewise seen to be older 

 than the Menevian, which, at St. John, includes material derived 

 therefrom. These ancient rocks are also largely represented in 

 Hastings County, Ont., where they occupy a position between the 

 Laurentian and the fossiliferous limestones of the Trenton group, and 

 are the equivalents of similar limestones and micaceous quartzites in 

 Berkshire County, Mass., and elsewhere in New England, which 



