106 REPORT 1859. 



seems to be that other curious algseform markings of the limestone are mere 

 infiltrations, 



On the Chronology of the Trap Rocks of Scotland. By A. Geikie, F.G.S. 



The points to be proved were— first, that there is sufficient abundance of felspathic 

 matter in the grits of the Silurian region of the Lammemioors to warrant the 

 inference that felspathic matter was either ejected during the formation of these 

 grits, or already existed in considerable abundance on the surface. Second, that 

 the Silurians of the Lammemioors are traversed by numerous dykes of felstone, 

 some of which may have been ejected during a contortion of the Lower Silurian 

 previous to the deposition of the Upper. Third, that the Old Red Sandstone period 

 was marked by powerful and long-continued volcanic activity, in several centres, as 

 the Sidlaws, the Ochils, the Pentlands, and part of the hills of Lanark. Fourth, 

 that the Carboniferous period was characterized by the especial abundance and 

 activity of its volcanic centres — so much so that there is not a well-defined zone of 

 carboniferous beds which does not, at some part of the Lothians, display its inter- 

 calated sheets of ash or greenstone ; but that these eruptions were markedly local 

 alike in their extent and in the character of the erupted material. Fifth, that after 

 the carboniferous series, there is a great gap in the chronology of the Scottish trap- 

 rocks, the next traces of subterranean movement being discernible in the lias of 

 Skye ; but that contemporaneous igneous rocks are not found until towards the top 

 of the middle oolite, where among estuarine limestones and shales, there occur in 

 Skye and adjacent islands enormous sheets of greenstone and basalt. Sixth, that, 

 as upper secondary rocks have still to be determined in the Hebrides, we have, at 

 present, to pass from the oolitic traps of Skye to the basalts and ashes of Mull, 

 which, as shown by their associated fossils, are tertiary, and probably miocene. 

 Lastly, that the later basalts and ashes of Arthur's Seat ought probably to be 

 referred to the later secondary, or older tertiary period. 



On Canadian Caverns. By George D. Gibb, M.D., M.A., F.G.S., 



Member of the Canadian Institute. 



The prominent feature of a large portion of the Province of Canada is the presence 

 of various limestone rocks belonging to the Silurian formations. Until lately, the 

 existence of caverns in these rocks, as well as in those lying subjacent, namely, the 

 Laurentian of Sir William Logan, was almost unknown ; but owing to the labours 

 of the Canadian Geological Survey, and of several private individuals, a number 

 have been discovered, at distances remote from one another, which it is the object of 

 the present memoir to notice. 



For convenience of description, these caverns are divided into two classes ; the 

 first comprises those which are at the present time washed by the waters of lakes, 

 seas, and rivers, including arched, perforated, flowerpot, and pillared rocks, which 

 have at one time formed the boundaries or walls of caverns, and all of them unques- 

 tionably the result of aqueous action. The second comprises caverns and subter- 

 ranean passages, which are situated on dry land, and, so far as we know, not attri- 

 butable to the same cause in their origin as in the first, or at least not applied in 

 the same manner. 



In the first class are included — 



1. Caverns in the shores of the Magdalen Islands. 



2. Caverns and arched rocks at Perc6, Gaspe. 



3. Gothic arched recesses, Gaspe Bay. 



4. The " Old Woman," or Flowerpot Rock, at Cape Gaspe. 



5. Little river caverns, Bay of Chaleur. 



6. Arched and flowerpot rocks of the Mingan Islands. 



7. Pillar sandstones, north coast of Gaspe. 



8. Niagara Caverns. 



9. Flowerpot Island, Lake Huron. 



10. Perforations and caverns of Michilimacinac, Lake Huron. 



11. The Pictured Rocks, Lake Superior. 



12. St. Ignatius Caverns, Lake Superior. : . 



