800 SIR J. W, DAWSON OK THE EOZOIC AND PALJEOZOIC 



in some parts of these old gneisses may be attributed to changes sub- 

 sequent to their original formation. The upper member contains 

 much limestone, with graphite and serpentine *, grej^ quartzites and 

 diorite. This last series, which I hold to be really Laurentian, as 

 it certainly underlies, and probably unconformably, the Huronian 

 system, must belong to the upper member of the series. There is, 

 indeed, nothing in its mineral character to exclude it from the Upper 

 Laurentian as developed farther west except the absence of certain 

 igneous rocks. 



The resemblance of this interrupted belt of Laurentian along the 

 Atlantic coast of America to that which extends southward from 

 Scandinavia along the west of Europe is patent to every observer. 

 The relation to the next succeeding formations is also identical, and 

 on both sides of the Atlantic those great foldings which have bent 

 and crumpled the old crystalline rocks seem to have occurred at the 

 close of the Laurentian and before the next succeeding formation. 

 It is to be observed here, however, that in the case of the Laurentian 

 these foldings pervaded the whole of what are now the Continental 

 areas, as well as those marginal lines which were alone affected by 

 the succeeding movements. This general disturbance of the Lau- 

 rentian over the whole breadth of our continents, and this before 

 any of the succeeding beds were deposited, impresses us with the 

 conviction that the earth-movements immediately following the 

 Laurentian were more extensive than those of any subsequent 

 period, that they form a sufficient explanation of the very different 

 character of the next succeeding formations, and that they produced 

 wide areas of elevated rock which formed the nuclei of all later de- 

 positions and movements. 



In comparing the Upper Laurentian of IS'ew Brunswick with the 

 rocks which elsewhere, as in New Hampshire f, the district of St. 

 Jerome, the Madoc district in Ontario, and the country west of Lake 

 Superior, rest on the older Laurentian gneisses or on rocks regarded 

 by some as primitive granites, one is obliged to admit either that 

 this formation is of a somewhat protean character, or that, as Hunt 

 maintains, there are several different formations of post-Laurentian 

 crystalline rocks occurring in these different localities. 



In the Lewisian gneiss of Murchison we have in Britain an ade- 

 quate representative of the Lower Laurentian, and in the two members 

 of the Dimetian of Hicks a sufficient parallel to the middle and 

 upper members of this great series J, which undoubtedly also appear 

 in the isolated mass of the Malverns, and have been recognized by 

 Barrois and Bonney in the ancient crystalline rocks of Brittany §. 



* In this limestone there occur fragments of Eozoon, and the graphite shows 

 obscure fibrous structures. 



t Hitchcock's Eeport. The beds called Montalban by Hitchcock occupy this 

 position. 



t Hicks's " Classification of Eozoic and Lower Palgeozoic Eocks," Popular 

 Science Eeview, 1881. 



§ Bonney, Quart. Journ. Geol. Soc. vol. xliii. 



