260 THE CANADIAN NATURALIST. [Vol. ix^ 



affinities) have not been reproduced to any great extent since the 

 beginning of paleozoic time. 



3d. The eruptive rocks, or at least a large part of them, are 

 softened and displaced portions of these ancient neptunean rocks^ 

 of which they retain many of the mineralogical and lithological 

 characters. 



II. The History of pre-Cambrian Rocks in America. 



Coming now to the history of our knowledge of American 

 crystalline rocks, we find that the lithological characters of the 

 Primary gneissic formation of northern New York were known 

 to Maclure in 1817, and were clearly defined in 1832 by Eaton, 

 who, under the name of the Macomb Mountains, described what 

 have since been called the Adirondacks, and moreover distin- 

 guished them from the Primary rocks of New England. Emmons, 

 in 1842, added much to our lithological knowledge of the cry- 

 stalline rocks of northern New York, but regarded the gneisses, 

 with their associated limestones, serpentines and iron-ores as all of 

 plutonic origin. Nuttall, who had previously studied the similar 

 rocks in the Highlands of southern New York and New Jersey, 

 had however maintained, as early as 1822, that these had resulted 

 from an alteration of the adjacent paleozoic graywackes and lime- 

 stones, into which he supposed them to graduate. This view 

 was, at the time, opposed by Vanuxem and Keating, but was 

 again set forth in 1843, by Mather, who while admitting the ex- 

 istence of an older or Primary series of crystalline rocks, con- 

 ceived a great part of these rocks in southern New York to be 

 altered paleozoic, and distinguished them as Metamorphic rocks. 

 To this latter class he referred all the crystalline stratified rocks 

 of New England, and ended by doubting whether a great part of 

 what he had described as Primary was not to be included in his 

 Metamorphic class. The subsequent labors of Kitchell and of 

 Cooke have however clearly established the views of Vanuxem 

 and Keating as to the Primary age alike of the gneisses and 

 the crystalline limestones of the Highlands. 



The similar gneissic series in Canada, which was known to 

 Bigsby and to Eaton as an extension of that of northern New 

 York, was noticed by Murray in 1843, and by Logan in 1847, 

 as pre-paleozoic, though apparently of sedimentary origin, and 

 hence, according to them, entitled to be called Metamorphic 

 rather than Primary. It was described by Logan in 1847, as 



