210 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



average inclination at 10°, gives a perpendicular thickness exceed- 

 ing 5400 feet. In this thickness are contained four seams of 

 workable coal, ranging from 4 to 7 feet each, and several small 

 seams of less than 2 feet. It may be satisfactory to the advocates 

 of Mr. Logan's theory of the formation of coal, to learn that all 

 the seams above mentioned, and in fact every one that I. have 

 examined in other parts of this coal-field, rest upon fire-clay floors, 

 containing leaves of Stigmaria. Vegetable remains, the same that 

 are usually found in the coal fields of Great Britain, are also met 

 with in great abundance ; and occasionally trunks of trees, from one 

 to two feet *in diameter, are found both in vertical and in horizontal 

 positions. Besides these, I have recently discovered fishes' scales, 

 with teeth, fins, bones, and coprolites in a bed of bituminous shale, 

 and in a thin seam of impure cannel coal. 



The great sandstone or millstone grit upon which the coal mea- 

 sures repose may be traced along the southern border of the coal 

 field of Sydney ; but its thickness is variable, for it is compressed 

 within very narrow limits at the western end, where the granitic 

 ridge of Cape Dauphin rises abruptly behind the carboniferous 

 limestone. The belt of limestone and gypsum which crosses Bou- 

 lardrie Island about two miles to the S.W. of the crop of the coal 

 measures, has apparently been brought up to the surface by a 

 fault, since the same beds of limestone show themselves occa- 

 sionally, cropping out from under the millstone grit, on both shores 

 of Boulardrie to its S.W. extremity, as is represented in the follow- 



ing section : — 



Section of the South-eastern Shore of Boulardrie Island, 26 miles 

 S.W. d 



Island Point § 



N. E. 

 Pt. Aconi. 



6. Coal measures. 3. Limestone. 



5. Millstone grit. 2. Limestone, gypsum, and shales. 



4. Limestone, gypsum, and marls. 1. Limestone and shales. 



On the eastern shore of the Little Bras d'Or Lake, we have a good 

 section of the millstone grit, from the crop of the coal measures to 

 the mountain limestone at George's River, 2000 feet in thickness. 

 The sandstones are generally coarse and pebbly ; but some of the 

 beds are compact and fine-grained, affording excellent building 

 stone ; false bedding is of frequent occurrence. A few beds of 

 shale are interstratified with the sandstones ; vegetable remains, 

 such as Calamites and Lepidodendron, are abundant ; and occa- 

 sionally small patches of lignite are seen. The millstone grit pre- 

 serves the same characteristics from hence to Miray Bay, where it 

 comes into contact with a coarse conglomerate, and is thrown into 

 a vertical position. One solitary Lepidostrobus was here found in 

 the sandstone, being the only one yet met with in the island. 



