XIII] GEOGNOSY OF THE APPALACHIANS. 281 



area of norites is found to occupy a position in contact with 

 rocks regarded as belonging to the Huronian and the White 

 Mountain series. The rocks which are referred to the Norian 

 series in the White Mountain region, according to Hitchcock, 

 rest upon the gneisses and mica-schists of the White Moun- 

 tains ; while these overlie unconformably a more ancient series 

 of granitoid gneiss, supposed to represent the Laureiitian. 



The hypersthene rock of Skye was by MacCulloch regarded 

 as an eruptive rock ; and Giekie, in his memoir on the geology 

 of a part of Skye, published in 1858 (Quarterly Journal of the 

 Geological Society, XIV. page 1), appears to include them with 

 certain syenites and greenstones, which he vaguely speaks of as 

 not intrusive, though eruptive after the manner of granites 

 (loc. cit., pp. 11-14). Specimens of these rocks from Loch 

 Scavig, and others in MacCulloch's collection from that vicinity, 

 which I have examined, are, however, identical with the North 

 American norites, whose stratified character is undoubted. I 

 called attention to these resemblances in the Dublin Quarterly 

 Journal for July, 1863 (ante, page 33); and Professor Haugh- 

 ton, of Dublin, who in 1864 visited Loch Scavig, subsequently 

 described and analyzed the norite from that locality ; which 

 is, according to him, evidently " a bedded metamdrphic rock." 

 (Dublin Quarterly Journal for 1865, page 94.) 



The distribution of the crystalline rocks of the Norian, 

 Huronian, and Montalban or White Mountain series would 

 seem to show that these are remaining portions of great, dis- 

 tinct, and unconformable series, once widely spread out over a 

 more ancient floor of granitic gneiss of Laurentian age ; but 

 that the four series thus indicated include the whole of the 

 crystalline stratified rocks of New England is by no means 

 certain. How many more such formations may have been laid 

 down over this region, and subsequently swept away, leaving 

 no traces, or only isolated fragments, we may never know ; but 

 it is probable that a careful study of the geology of New Eng- 

 land and the adjacent British Provinces may establish the ex- 

 istence of many more than the four series above enumerated. 

 When it is considered that we find within the limits of southern 



