Henry Hicks — On the Northern Palceozoic Rocks. 157 



tions indicate parts only of what were probably two great continents 

 extending over those areas, separated from one another by an inter- 

 mediate ocean, narrower considerably than the present Atlantic, but 

 still occupying part of the basin. When these continents commenced 

 to subside, the parts facing the Atlantic were the first to become sub- 

 merged. On the European side this is evident from a consideration of 

 the sediments, and also in the faunas (of which I shall have to speak 

 more fully in anotlier part of the paper) ; and it seems tolerably clear 

 that such was also the case on the American side. I have attempted 

 to explain in another paper ^ the lines of depression along which the 

 waters gradually encroached, and endeavoured there to show that the 

 contraction must at this time have taken place along two well-de- 

 fined lines, or that the continents, before they began to subside, had 

 for the most part a sloping surface with the higher plateaux to the 

 north-east on the European, and to the north-west on the American 

 side. As also at a later period in the Palseozic age parts of these 

 old continents were above water-level, when contiguous areas were 

 submerged to a great depth, it is evident that they were traversed 

 by mountainous ranges of great height. Some portions of this old 

 land now visible to us in Western Europe were undoubtedly brought 

 up to the surface from a very great depth at the close of the Palaso- 

 zoic, whilst others, upon equally certain evidence, could not have 

 been but at a slight depth at that time, and some probably not even 

 then submerged. This condition of continents of great size in high 

 latitudes, with elevated plateaux and high mountains, would lead us 

 to believe that they were covered with ice and snow in their higher 

 parts, and that the plains and valleys had therefore much loose 

 material strewn over them. In the Cambrian rocks in Wales 

 boulders of considerable size, sometimes a foot in diameter, are often 

 found in the beds of conglomerate, and the frequent alternations of 

 conglomerates, grits and sandstones, seem to prove that, at least in the 

 earlier epochs, an abundance of loose material must have been near 

 and ready at hand to be easily denuded off as each part became sub- 

 merged. Marine action on the hard metamorphic cliffs alone could 

 scarcely have produced so much sediment. Moreover, the enormous 

 thickness found with scarcely a trace of any beds heaped up by 

 marine life at this period, either in the American or European areas, 

 as may be seen by reference to the Table, show conclusively that an 

 additional force must have been at work. In some places, also, the 

 sediments were heaped up so rapidly, that during a depression of 

 several thousand feet the rate seems only to have kept pace with 

 the accumulations, and shoal conditions continued to prevail during 

 the whole time. As the depression went on, the areas first sub- 

 merged received only such materials as could be carried a consider- 

 able distance, and hence finer deposits are found over these, whilst 

 in the more immediate regions of the still unsubmerged lands, the 

 rougher materials continued to be heaped up. We find, therefore, 

 contemporaneous deposits formed to some extent of very different 

 materials, and varying considerably in thickness. After the close of 

 1 Quart. Journ. Geol. Soc, JSTov. 1875. 



