242 C. LAPWORTH ON THE MOFFAT SERIES. 



description. The rugged cliffs of the "Berwickshire coast, where these 

 convoluted rocks frown over the North Sea, have been familiar to 

 geologists since the days of Hutton and Hall. In the inland dis- 

 tricts we meet upon every traverse an endless succession of strata 

 dipping constantly in the same general direction, and presenting us 

 with the fallacious appearance of an almost interminable thickness 

 of similar deposits. 



The dominant rock of the Southern Uplands is a gritty or coarse- 

 grained grey wacke, sometimes grey or green, at other times of a deep 

 purple colour. It is associated with beds of fissile flagstone of simi- 

 lar tints, which either alternate with the greywackes or occur alone 

 in zones of great thickness. These two types of rock everywhere 

 preponderate, and usually prevail to the exclusion of every thing 

 else. Occasionally, however, they are relieved by masses of pebbly 

 conglomerate, breccias, or boulder-beds ; but these are very variable 

 in character and local in occurrence. 



Excluding from our present consideration the strata recognized as 

 being unequivocally of Upper Silurian age, it is in one district only 

 that the beds of this wide-spreading rock-group approximate in 

 their general characters to the type familiar to us in the classic 

 ground of Siluria. On the west coast, in the neighbourhood of the 

 town of Girvan, limestones, shelly sandstones, and mudstones yield 

 fossils in extraordinary profusion, and, both mineralogically and 

 palseontologically, remind us strongly of those of the most prolific 

 areas of Wales and Shropshire. 



A fauna similar in its broader features to that afforded by the 

 Girvan beds, but far inferior in richness and variety, characterizes 

 the calcareous zones in the conglomerates and breccias of Peebles, 

 Lanark, and Dumfries. 



A totally distinct group of fossils, and one hitherto regarded as of 

 little geological significance, occurs in certain beds of black carbona- 

 ceous shales and mudstones, which, in many districts, occupy long 

 lenticular or boat-shaped areas in the great mass of barren grey- 

 wacke. These peculiar beds appear quite unexpectedly and as sud- 

 denly disappear ; but, when laid down upon the map, they are seen 

 to form extended moniliform lines, often many miles in length. Tbey 

 are found at intervals throughout the northern half of the Uplands, 

 from the Irish Channel to the North Sea, and everywhere swarm 

 with Graptolites in extraordinary profusion. 



The striking mineralogical features of these black bands, their 

 prolific fauna, and their great longitudinal extent, where for thousands 

 of square miles no other continuous stratum, separable either bylitho- 

 logicalorpalseontological characters, relieves the wearisome monotony 

 of the interminable greywackes, soon convince the geologist that it 

 is by their aid alone that he can ever hope successfully to unravel 

 the more than ordinary complexity of the South-Scottish succession. 



In seeking to elucidate the geological structure of the Southern 

 Uplands, these Graptolitiferous strata naturally claim our first atten- 

 tion. It is impossible to clear up all the difficulties in which they 

 are enshrouded within the limits of a single memoir. In the present 



