287 



begins, however, to be subdivided by thick masses of sandstone and 

 carbonaceous shale, of which we had hardly a trace in Yorkshire; and 

 gradually passes into a complex deposit, not distinguishable from 

 the next superior division of the series. Along with this gradual 

 change is a greater development of the inferior coal-beds alternating 

 with the limestone ; some of which, on the north-eastern skirts of Cum- 

 berland, are three or four feet in thickness, and are now worked 

 for domestic use, with all the accompaniments of rail-roads and 

 steam-engines. 



The alternating beds of sandstone and shale expand more and 

 more, as we advance towards the North, at the expense of all the 

 calcareous groups, which gradually thin off, and cease to produce 

 any impress on the features of the country. And thus it is, that 

 the lowest portion of the whole carboniferous system, from Bevv- 

 castle Forest along the skirts of Cheviot Hills to the valley of 

 the Tweed, has hardly a single feature in common with the inferior 

 part of the Yorkshire chain ; but, on the contrary, has all the most 

 ordinary external characters of a coal formation. Corresponding 

 to this change, is also a gradual thickening of carbonaceous matter 

 in some of the lower groups. Many coal works have been opened 

 upon this line; and near the right bank of the Tweed (almost on a 

 parallel with the great scar limestone) is a coalfield, with five or six 

 good seams, some of which are worked, not merely for the use of 

 the neighbouring districts, but also for the supply of this capital. 



The beds of sandstone, shale, and limestone, forming the base of 

 the carboniferous system in the basin of the Tweed, are often deeply 

 tinged with red oxide of iron, and have been sometimes compared 

 with the new, and sometimes with the old red sandstone. To the 

 new red sandstone they have unquestionably no relations ; and I 

 should rather compare them (especially as the old red sandstone of 

 the North of England seldom exists but as a conglomerate, and is 

 seen in that form on the flanks of the Cheviot Hills) with the red 

 beds of mountain-limestone and sandstone, which, both in Cumber- 

 land and Lancashire, sometimes form the base of the whole carbo- 

 niferous series. 



Such are the remarkable changes of our carboniferous system in 

 its range from the Bristol Channel to the Scotch border : and it re- 

 appears on the north-side of the great greywacke chain of that country 

 with so many points of analogy, that we must, I think, regard the 

 coal measures in the neighbourhood of Edinburgh as part of a 

 very ancient deposit, nearly of the same age with that on the banks of 

 the Tweed*. 



Thus it appears, from what has been stated above — that tree 



* The general relations of the various groups of the carboniferous system of 

 Northumberland, are, on the whole, very faithfully represented in the geological 

 map of that county, published some years since by Mr. Smith. A very detailed de- 

 scription of a portion of the carboniferous series of the Tweed was read during the 

 past year, by Mr. Winch, before the Philosophical Society of Newcastle, and has 

 been since published. [See Phil. Mag. and Annals, N. S. vol. ix. p. 11.] Another 

 paper, on the same subject (which I did not see till these sheets were passing 

 through the press), has been recently published by Mr. Witham of Edinburgh. 



