The Correlation of Geological Structure. 405 



coast, and that neglect of this had led to serious miscon- 

 ceptions. 



The rugged islands of Laurentian and Huronian rocks 

 correspond on both sides of the Atlantic, and show an 

 identity of succession in deposits as well as a sychronism 

 of the great folds and lateral pressures which have disturbed 

 these old formations. The Cambrian sediments and fossils 

 as originally described by Hartt, and more recently and in 

 so great detail by Matthew, are in close correspondence 

 with those of Wales and not identical with those of internal 

 America. The recent paper of Lapworth on the Grapto- 

 lites affords evidence of the same kind, and shows that these 

 were Atlantic animals in their time. It also throws much 

 additional light on the Quebec group of Logan considered 

 as an Atlantic marginal formation, representing a great 

 lapse of time in the Cambrian and Ordovician periods. 

 The author had long ago shown that the Siluro-Cambrian or 

 Ordovician of Nova Scotia conformed more nearly to that 

 of Cumberland and Wales than to the great limestone for- 

 mations of Quebec, Ontario and New York. The Upper 

 Siiurian also is of the type of that of England and Wales, a 

 fact very marked in its fossil remains as well as in its 

 sediments. 



The parallelism in the Erian or Devonian in both coun- 

 tries is most marked, both in rocks and fossils, and while 

 this is apparent in the fishes, as worked up by Mr. White- 

 eaves, it is no less manifest in the fossil plants as described 

 by the author. 



The Carboniferous, in its limited troughs, the character 

 of its beds, and its fossil animals and plants, also points to 

 a closer relationship in that period between the two shores 

 of the Atlantic than between the Atlantic coast and the 

 inland area. This was evidenced by comparative lists of 

 species. 



The Trias of Nova Scotia and of Prince Edward Island, 

 as the author had shown in 1868, 1 resembles that of Eng- 

 land very closely, in its aqueous deposits and in its asso- 

 ciated trappean rocks. 



1 Journal of Geol. Society of London, Vol- VI. 



