138 Rev. W. D. Conybeare on a Geological Map of [Feb. 



in any part of the island displayed, inasmuch as all the beds of 

 that formation come indifferently into contact with the super- 

 strata. It is possible that were those highest beds visible, they 

 might be found to exhibit a gradual transition (as is the case in 

 so many otherinstanc.es) into the characters of the next sandstone 

 series. If we are to refer the rotheliegende to the coal forma- 

 tion in any manner, it can only be in considering it as thus inter- 

 mediate in place and character between the regular coal mea- 

 sures and the sandstones of the next ajra. To identify it in any 

 way with the lowest beds of the whole system is to invert, every foun- 

 dation of geological arrangement, and to unsettle all those princi- 

 ples to which the science owes its present precision. 



Distribution or the Carboniferous Series. 

 (A.) Coasts of the Baltic. 



Following the same course which was pursued in indicating 

 the distribution of the ancient chains, we may first trace the 

 coal formation, where it appears to rest against the most north- 

 erly of these chains, that of Scandinavia. 



In this line, we find coal in the island of Bornholm. and again 

 in Sweden on tiie south of the primitive tract near Helsingborg, 

 at the mouth of the Baltic. 



(B.) Scotland. 



If we regard the Grampian mountains as a prolongation of the 

 Scandinavian chains, the great coal district of Scotland must also 

 be considered as similarly related to those above-mentioned. 

 It occupies the tract forming what may be called the great 

 central valley of Scotland (speaking relatively, for considered in 

 itself its surface is very considerably varied), which lies between 

 the great transition chain on the south, and the still loftier primi- 

 tive ranges of the highlands on the north. The whole of this 

 wide tract is occupied by the coal measures, the carboniferous 

 limestone, and the old red sandstone, associated in every possi- 

 ble manner with vast accumulations of every variety of trap. 



In the low district on the east of Sutherland, where the 

 secondary formations again intrude among the primitive high- 

 land chains, coal has been discovered at Brora; but from the 

 slight description incidentally given of this tract in the memoir 

 of Mr. Bald (vol. iii. Trans. Wern. Soc), before referred to, it, 

 may be conjectured that this does not belong to the principal 

 coal formation, but to those beds which occasionally occur in 

 more recent formations, being, perhaps, of the same sera with 

 the coal of the Cleaveland district in Yorkshire. 



In Dumfrieshire, near the southern or transition chain of 

 Scotland, we find many limited coal-fields reposing against, or 

 forming narrow basins in, the valleys of the latter chain ; these 

 are associated with, and rest upon as usual, thick beds of the 

 carboniferous limestone. 



