COMPARISONS WITH OTHER COUNTRIES. 91 



geological history of the region now included in the maritime pro- 

 vinces. They establish what I could then only indicate as probable, 



that the great igneous outbursts of the Devonian age, at mpanied 



with profound alteration of the older sediments, with much disturb- 

 ance of these beds, and the introduction into them of mineral veins. 

 were preceded by a long series of emissions of trachytie lavas and 

 volcanic ashes and breccias, now represented by the felsites, porphyi ies, 

 and agglomerates of the lluronian, Cobcquid, and Mascarene series. 

 Beginning with the lluronian age, these eruptive actions were inter- 

 rupted in the Cambrian, but recurred with great intensity in the Lower 

 Silurian, and extended into the Upper Silurian age. For this reason, 

 the rocks of these periods in the Acadian area present a marked 

 lithological contrast to those which were accumulating at the same 

 time in the great quiet sea areas of the interior of the continent, and 

 it becomes extremely difficult to correlate these deposits in detail. 

 The peculiar characters of the Quebec group of Eastern Canada, and 

 of the rocks called Taconic by Emmons further south, are no doubt 

 connected with the great igneous actions of the Lower Silurian age. 

 We may ultimately find that in the Silurian period the Atlantic coast of 

 America Avas the theatre of igneous activity comparable with that 

 which has prevailed in later periods on the Pacific coast, and that the 

 relations of the coastal and interior rocks are similar to those between 

 the Mesozoic porphyrites and trachytes of British Columbia, and 

 the contemporaneous shales, marls, and sandstones of the interior 

 plains.* 



It is to be observed here that the character of the older deposits 

 in the Acadian area has been modified not only by contemporaneous 

 igneous action, but by the action of the Arctic currents in drifting 

 along the Atlantic border earthy matter set free by frost ami 

 aqueous denudation in the north ; as well as by the metamorphic 

 influence connected with the subsequent igneous ejections of the 

 Devonian. 



It is further to be observed, that the peculiar features above re- 

 ferred to ally the rock formations of the Silurian age in Nova Scotia 

 and New Brunswick with those of Great Britain, in which also there 

 are great series of bedded volcanic rocks and ash rocks both in 

 Cumberland and Wales. A rough equivalency may, indeed, now 

 be traced in these rocks on the two sides of the Atlantic, as repre- 

 sented in the following table : — 



* See on this subject a paper by Mr G. M. Dawson, On Mesozoic Volcanic Hocks 

 of British Columbia, Geological Magazine, July 1877. 



