386 



THE AZOIC SYSTEM AND ITS SUBDIVISIONS. 



'* 3. Poriihyritic Granite. 



*' Common granite full of large crystals of feldspar Some portioiia 



of it have evidently been injected, while the arrangement of the feldspathic 



crystals in parallel lines leads to the suspicion of stratification in other cases." 



*'4. Common Granite. 



*' The granite of New Hampshire seems to have originated at five different 

 periods. First are the {a) indigenous and (6) eruptive granites of the AVhite 

 Mountain series ; second, the (c) indigenous granites of the Merrimack group, 

 in which none of the eruptive class have yet been seen ; third, the Ql) iudige- 

 nous and (c) eruptive granites of the Coos and calciferous mica scliist groups." 



*' 5. Merrimack Group. 



*'They probably belong to the earliest Silurian series." 



*' 6. Quebec Group. 



*' Lower Silurian^ according to Sir William E. Logan." 



** 7. Coos Group of slates, schists, quartzites, etc. 



"■ It ai)pears cleaily to overlie the White Mountain veins un conformably." 



" 8. Calci/crous Mica Schist. 



*' 9. Claij Slates. 



"8 and 9 seem to be limited outliers in New Hampshire." {I. c, pp. 31-34.) 



In the Third Report, for the year 1870, it is stated that 



** the White Mountain rocks are believed to belong to two great systems, the 

 Gneissic and the Coos Group. The first are, for convenience, called the White 



Mountain scries These rocks appear to underlie the Coos group, and 



are therefore older. The presumption is that they are entirely Eozoic, tliough 

 it is not clear whether they are to be considei'ed as the equivalent of tlie Lau- 

 rentian of Canada, or more nearly tlie age of the Cambrian of Great Britain as 



restricted by the Government Survey Its satisfactory reference to 1be 



Eozoic series will enable us to clear up the obscurities of New Hampshire 

 geology." 



The Coos group was phiccd as before above the White Mountain 

 series, and, '^ judging from fossils in Nova Suotia, this group is not far 

 from the St. Johns slates in age." (/. c, pp. 9-11.) 



In the next Report, — that for the year 1871, —some changes were 

 made in the general arrangement of the rocks, which were classed as 

 follows : — 



" 1. Porphyritic Gneiss. 



" We suppose this to be tlie oldest formal ion among the mountains. Geolo- 

 gists speak of a rock of this cliaracter as common in the laurentian in various 

 parts of North America and Europe." 



