19C) NOTES OX THK GEOLOGY OF EAST LOTIIIAX AND UERWICKSHIRE. 



Section as scon from the opposite side of the ravine, about one hundred feet hi^h. a, unconformable 

 beds of Old Red Sandstone; ft, vertical beds of Silurian strata. These beds of the Old Red are the finer 

 quartzose Sandstone. 



attrition by the action of water. The fragments of quartz, however, present 

 an exception to this rule, being of two kinds; first, well rolled and polished 

 pebbles, possibly originating in some distant and ancient mass of quartz, which 

 has now disappeared; second, angular fragments which seem to have been 

 imbedded in the conglomerate immediately after they were detached from the 

 parent mass. These last probably proceeded from the larger veins of quartz 

 so numerous in the slates and schists, the softer materials in which they occur, 

 forming part of the cement which binds the conglomerate together. The 

 fragments of the schist are also very angular and sharp. Another appearance 

 which the Old Red Sandstone presents along a great portion of the coast, at 

 all events from 8iccar to the Cove, and which I think proper to notice here, 

 is, tliat in its conglomerate form it frequently alternates with narrow beds of 

 finer Sandstone, These alternations have sometimes been supposed to indicate 

 partial elevations and subsidences in the bed of the sea where the materials 

 were deposited; but from their frequency, it seems much more probable that 

 they ought to be attributed to the periodical increase and diminution of 

 those currents or streams which bore the gravel to the ocean. 



At Siccar we have the northern junction of the newer Palaeozoic rocks with 

 the older of the Lammermuir ridge; and at St. Abb's Head, near Coldingham, 

 which I had the pleasure of seeing last July, we have the southern junction, 

 but the immediate contact is not visible; the Lammermuir Hills running east 

 and west. The section which the sea coast makes at St. Abb's is highly 

 instructive, from the great disturbance of the older strata, and the variety of 



