VERMONT AND WESTERN MASSACHUSETTS. 455 



alban' or 'White Mountain series' in New Hampshire, and regarded of pre- 

 Silurian age, are here included, and are hence nothing liut altered Helderberg 

 sediments. It is hence far from true that ' the crystalline rocks of the Green 

 Mountain and White Mountain series ' and ' the whole of our crystalline schists 

 of Eastern North America are not only pre-Silurian, but pre-Cambrian in age.'" 



In the same article (p. 341) Professor Dana further remarks : — 



" Lithological evidence of a geological age among metamorphic rocks of dis- 

 tant regio7is is in general worse than worthless. It is easy to use, and presses 

 itself on the mind most insinuatingly when a conclusion is eagerly wanted. 

 .... I have further found that the Earth did not finish up its metamoqjhic 

 work in pre-Silurian time, or even by the epoch closing the Primordial, as it 

 did not its mountain-making." 



For the field evidence upon which Professor Dana founded his con- 

 clusions, the reader is referred to the original article. 



In the Report of Progress of the Canada Geological Survey, for the 

 year 1873-7-1, Mr. Selwyn remarks that considerable doubt and uncer- 

 tainty have been thrown upon the labors of Sir William Logan by arti- 

 cles from the pen of Dr. Hunt. These articles appear to the present 

 head of the Canada Survey to indicate that the earlier views of Dr. 

 Hunt in regard to the true stratigraphical positions of the rocks in 

 Eastern Canada had undergone an almost entire revolution. This 

 change of opinion is said by Mr. Selwyn to have been based, so far as 

 he could understand it, on lithological comparisons exclusively, and he 

 thus expresses his views in regard to that kind of evidence : — 



*' Whether the relative ages of great masses of crumpled and metamorphic 

 strata can be thus determined apart from, or in the absence of palaeontological 

 and stratigraphical evidence, is a question which, as a stratigraphist of thirty 

 years' experience, I should decidedly answer in the negative. The degree and 

 character of the metamorphism and mineralization which a group of strata 

 exhibit, cannot be relied on as certainly indicative of geological antiquity, and, 

 as tending to strengthen this opinion, the recent researches of Mr. Ptichardson 

 in British Columbia have shown that epidotic, chloritic and serpentinous rocks, 

 •with crystalline limestones and magnetites, are as characteristic of upper palae- 

 ozoic, and perhaps also of even later formations when they have been subjected 

 to an equal amount of plication and folding, as they are of the oldest palneozoic 

 and protozoic strata, such as those of Eastern Canada and the New England 

 States." 



In 1875 Prof J. P. Lesley stated that in Pennsylvania the Hnronian 

 or Green Mountain series was seen to overlie the White Mountain 

 series; while he iinqualifiedly placed both series in Vermont and New 

 Hampshire below the Potsdam. (Second Geological Survey of Pennsyl- 

 vania, D., pp. Go, 66.) 



