CAKBONIl-'KKOUS DISTRICT OF CUMBERLAND. 



L53 



carefully detailed section as our guide, we see in the low cliff and in the 

 shore-reefs beds of reddish and gray sandstone, alternating with red- 

 dish shales or beds of hardened and laminated clay. In a few places 

 we find among these beds layers of gypsum and of a coarse sandy 

 limestone. In several of the gray beds there are fragments of trunks 

 and branches of trees, converted into coal, and resembling, what they 

 certainly once were, drift trees embedded in sand-banks. Associ- 

 ated with these remains, we find in four of the beds small quantities 

 of the gray sulphuret and green carbonate of copper, minerals intro- 

 duced into these beds by waters holding sulphate of copper in solution, 

 which the carbonaceous matter of the fossil wood has deoxidized, and 

 thereby caused its deposition. Such appearances are not infrequent in 

 beds containing fossil plants, but they have not hitherto been found to 

 afford sufficient quantities of copper to be of any practical value. I 

 may also remark here, in connexion with the occurrence of fossil plants 

 in gray rather than in red beds, that in the coal formation, as in the 

 modern marshes and peat-bogs already described, the presence of 

 vegetable matter has often destroyed the red colour of beds tinged with 

 peroxide of iron, and hence the fossils are in some sense the cause of 

 the gray colour of the beds in which they are found. Beds of the 

 kinds just described occupy the shore to a distance equal to 2308 

 feet, as ascertained by the careful measurements of each bed made by Sir 

 W. E. Logan. I may remind the reader, that as these beds dip to the 

 south-west, we are constantly proceeding from older to newer beds. 



In the succeeding 3240 feet of beds we find a similar series, with 

 some additional features indicating our approach to the great masses 

 of fossil vegetables entombed in the true coal measures which overlie 

 them. There are here nine seams of coal, all very thin, their total 

 thickness being only ten inches ; and under each seam we observe a 

 bed of clay or crumbling argillaceous sandstone, with remains of roots 

 belonging to plants to be noticed hereafter, and which had much to 

 do with the accumulation of the coal. We find also in this thick 

 .-erics of sandstones and shales several bands of hard black limestone, 

 yielding a bituminous and almost animal smell when rubbed or struck, 

 and containing abundance of little diamond-shaped plates with smooth 

 and polished surfaces, which, if we are acquainted with the animals of 

 the Coal period, we recognise as the scales of a singular tribe of fish, 

 the Ganoids, of which numerous species abounded in the Carboniferous 

 period, but which are now represented in America only by the bony 

 pikes of the Canadian lakes, and a few other fresh-water fishes. There 

 is also in this part of the section a far greater prevalence of gray sand- 

 stones than in the part previously noticed, and in these gray sandstones 



L 



