302 Mr. MuRCHisoN on the Coal-field of Brora in Sutherlandshire, 



coal to be analogous to that of the Eastern Moorlands of Yorkshire, altlrough 

 the extraordinary thickness of the former, compared with any similar deposit 

 of the latter, (which never exceeds from 12 to 17 inches,) might have formerly 

 led to the belief that it was a detached and anomalous deposit of true coal, 

 rather than a lignite of any of the formations above the new red sand- 

 stone : such misconception might more easily arise at a period when the strata 

 were not identified by their fossil organic remains. 



An epitome of the history of these coal-works is given in the Appendix, 

 p. 323 *. 



Coast Section. 



I will now briefly describe the appearances on the coast, proceeding from 

 S.W. to N. E. ; as the beds exposed at ebb-tide, and in the low-cliffs, best ex- 

 plain the general stratification of the district. 



The shore between Loch Fleet and Golspie consists exclusively of blown 

 sand ; and although the interior to the westward is very soon occupied by the 

 red conglomerate, there are no traces of it upon the coast. 



The first appearances of those strata which alternate throughout the Brora 

 district, are seen at low water near Dunrobin Castle, where calcareous sand- 

 stones are succeeded by beds of pebbly calciferous grit, (upon which the 

 pier is built,) and which are overlaid by shales containing limestone with 

 fossils. The coarser varieties of the calciferous grit have in a remarkable 

 degree that structure which is so frequently observable in all concretionary 

 rocks ; the planes of fracture coinciding with the cleavage of the grains of 

 which the mass is chiefly composed, and exhibiting a silky lustre in one direc- 

 tion. The beds on this part of the shore occupy from 400 to 500 yards in 

 breadth, with a N. E. dip of about 20° or 25°. The grits are overlaid by 

 sandstone and micaceous shales, the latter containing numerous and flat- 

 tened impressions of ammonites and small belemnites with indications of coaly 

 matter. These are succeeded by black and white sandstone and shale, inclu- 

 ding a dark coloured limestone, the latter being an aggregate of fossils, inclu- 

 ding gryphaBa nana, terebratula inconstans, serpula, pullastra, plagiostoma, 

 pecten, &c. &c. The highest shales contain a dark blue limestone with 

 septaria and very small sack-shaped pyritous nodules. 



* For these documents and much kind assistance during the prosecution of my inquiry, I am 

 indebted to the Marquess and Marchioness of Stafford, to whom belong all the tracts of country 

 laid down upon the map ; and their agent at the Brora works, Mr. Robertson, was most zealoui 

 in aiding my examinations. 



