Geological Society. 287 



the former instances, we also find the millstone-grit occupying an 

 intermediate position. The millstone-grit, however, becomes a very 

 complex deposit, with several subordinate beds of coal j and is sepa"- 

 rated from the great inferior calcareous group (known in the North 

 of England by the name of scar lime-stone), not merely by the great 

 shale and shale -limestone, as in Derbyshire, but by a still more com- 

 plex deposit, in some places not less than 1000 feet thick ; in which 

 five groups of limestone strata, extraordinary for their perfect con- 

 tinuity and unvarying thickness, alternate with great masses of 

 sandstone and shale, containing innumerable impressions of coal 

 plants, and three or four thin beds of good coal extensively worked 

 for domestic use. 



In the range of the carboniferous chain from Stainmoor, through 

 the ridge of Cross Fell, to the confines of Northumberland, we have 

 a repetition of the same general phenomena. On its eastern flanks, 

 and superior to all its component groups, is the rich coal-field of 

 Durham. Under the coal-field, we have, in regular descending order, 

 the millstone-grit, the alternations of limestone and coal measures 

 nearly identical with those of the Yorkshire chain, and at the base of 

 all is the system of the great scar limestone. The scar limestone 

 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 Bew- 

 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 j and 1 

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



the 



