In a recent article Gregory and Barrett1 state that the Keewatin and Timiskaming are approximately or completely contemporaneous. They further state that their contention is supported by the order of the pre-Paleozoic succession in Scotland as well as by that in several areas in Canada. Probably without fully appreciating the magnitude of the problems confronting the worker in the Canadian Shield, where the formations are so highly metamorphosed, and the Keewatin-Timiskaming areas, that have been studied in detail, are so widely separated from one another without connecting links, these writers give somewhat the impression that the Canadian classification of the older pre-Cambrian rocks is in a state of confusion.

In some areas in the Canadian Shield there is difficulty in distinguishing volcanic rocks which are more or less common to these two series or systems, but in most areas there is a fairly distinct break between them. This break . . .

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