178 THE CANADIAN NATURALIST. [Vol. i 



IX. 



find similar changes in the Chazy near Grenville. A third sug- 

 irestion is, that in order to understand the eastern members of 

 the Lower Silurian, it is necessary to be acquainted with the 

 contemporaneous igneous ejections mixed with these rocks, and 

 if possible to distinguish them from those of similar character so 

 largely present in the Huronian. This I have attempted, though 

 with only partial success, to effect for the Acadian Provinces. 

 Another, to which Dr. Hunt has directed attention in his recent 

 report in connection with the Survey of Pennsylvania, is the 

 importance of inquiry as to which of the many successive move, 

 ments and plications of the earth's crust occurring in palaeozoic 

 time, have most seriously affected the now so greatly plicated 

 and disturbed rocks of the Quebec group. Still another, and 

 one of the most important, is the study of the various kinds of 

 alteration which these rocks have undergone. We have m eastern 

 Canada rocks as young as the Devonian which have been sensibly 

 affected in this way, and there can be no doubt that large areas 

 of the Quebec group have suffered similar changes, and that on 

 the one hand it is possible that these metamorphosed portions 

 have baen confounded with older series, or that on the other 

 these older series have been inadvertently mixed with them. 



The value to be attached to fossils is another point of much 

 importance. Long experience has convinced me that in the 

 Cambrian and Silurian ages this kind of evidence is the most 

 conclusive of all ; but then it must be rightly understood. As 

 already observed, we must discriminate the animals characteristic 

 of the cold Atlantic waters loaded with Arctic sediment, from 

 those of the sheltered continental plateau. We must also bear 

 in mind that oceanic and probably floating forms of low grade, 

 like the Graptolites, have an enormous range in time, as com- 

 pared, for example, with the Trilobites, and the same remark 

 applies to some mollusks proper to sandy or muddy bottoms, like 

 the Lingulae and their allies, as compared with other mollusca. 



All these precautious must be taken in the study of these 

 rocks, and it involves no depreciation of the geologists above- 

 mentioned, to say that the different conclusions at which they 

 have arrived, depend very much on the different degrees of 

 importance which they have attached to the various kinds of 

 evidence accessible. 



One word, before closing, respecting names. These are of little 

 importance in themselves, but it is of consequence that they 



