14*2 Notes on the Geology of Murray Bay. 



tian forms irregular masses in the middle ground, and Cape Heu 

 presents its bold front in the distance. 



2. Silurian System, 



These rocks rest unconformably on the old gnarled Laurentian 

 beds, and are here sandy in the lower part, simulating the ap- 

 pearance of the Potsdam sandstone, seen in a similar position fur- 

 ther west. A little higher they assume the aspect of Calcareous 

 sandstones, and these are overlaid by limestones capped by dark 

 calcareous shales. We thus have a series which at first sight 

 might be supposed to be a miniature representation of the whole 

 lower Silurian of Canada, from the Potsdam sandstone to the 

 Utica slate. According to Mr. Uillings, however, the fossils of 

 these beds belong to the middle part of this series, between 

 the Chazy limestone and Trenton limestone, so that here the older 

 members of the Lower Silurian series either do not occur or are 

 represented only by a few feet of sandstone, nearly destitute of fos- 

 sils. This corresponds with a conclusion arrived at by Sir William 

 Logan, as the result of very extensive observation, that in the early 

 part of thfe Silurian period, the old Laurentian shore running 

 along the north of Canada was sinking beneath the sea, which was 

 gradually carrying the newer deposits further and further up its 

 sides, so that the older beds are often concealed from view. The sub- 

 sidence must have been greater in some places than in others, or 

 the upper deposits have in some places been more removed by 

 subsequent denudation, for while in the middle of Canada near 

 the confluence of the Ottawa, the series is complete, both to the 

 westward and eastward the older members of the Silurian series 

 are concealed. I was much struck with this lately at Madoc in 

 Upper Canada, where the junction of hard slaty rocks of the Lau- 

 rentian series with a Lower Silurian limestone is well seen. The 

 latter under the limestone presents a shattered and weathered sur- 

 face that must have long endured the action of the elements, 

 while the limestone, a mass of fragments of shells and corals, con- 

 tains irregular fragments of the older rock, and has filled up the 

 crevices of the latter with whole and broken Orthoceratites, and 

 other shells, which lie just as the wave threw them in. It re- 

 quires scarcely any imagination in such a place to fancy one's self 

 standing on the old Laurentian shore, and watching the bright 

 billows hurling their load of shells and fragments against the 

 shore, and year by year reaching higher and higher on the land, 



