256 C. LAPWOKTH ON THE MOFFAT SEK1ES. 



are reversed in position, and their relations are complicated locally 

 by visible faults and convolutions. 



Continuing our section beyond the zone last described, we come 

 immediately upon beds of a totally distinct character from any of 

 the Hartfell Shales. These strata constitute a band of hard thick- 

 bedded black flags, forming the highest ledge of the Long Cliff, and 

 standing up almost on end like a broad wall. Their appearance and 

 behaviour instantaneously call to mind the conspicuous D.-vesiculosus 

 bands of the Birkhill Shales ; and their identity with them is soon 

 placed beyond question by the detection of numerous examples of 

 Diplograptus vesiculosus, and its constant associates Climacograptus 

 innotatus and Monograptus tenuis. 



Between this band and the thin-bedded D.-Clingani zone of the 

 summit of the cliff must necessarily occur a fault of some magnitude, 

 as almost all the Hartfell shales, and several of the Birkhill zones, 

 are missing from between them. This, as we shall presently ascer- 

 tain, is a portion of the most important fault in the rocks of the 

 glen. 



At the eastern foot of the wall formed by the D.-vesiculosus band 

 lies the shivery D.-acuminatus band, dipping below the former in the 

 same attitude as in the Main Cliff. It swarms with its characteristic 

 fossils, and affords several excellent exposures of the peculiar gin- 

 gerbread-coloured bed at its base. 



This zone reposes immediately upon the six-foot mudstone of the 

 D.-anceps zone, which forms a pale band running obliquely up the 

 Long Cliff for some distance, very conspicuous among the dark 

 shales by which it is surrounded. It is underlain in its turn by the 

 f ossiliferous and variegated portion of the D.-anceps band, admirably 

 exposed, and swarming with Dicellograptus anceps, Climacograptus 

 tuber culatus, &c. 



Between this point and the great fault at the summit of the 

 cliff these three zones of D. vesiculosus, D. acmninatus, and Dicello- 

 graptus anceps are arranged in the same order as in the Main Cliff, 

 and have a corresponding dip to the west. But passing upwards 

 beyond the D.-anceps zone the sequence becomes greatly confused ; 

 the rocks are so convoluted and shattered that any attempt to unravel 

 them along this line appears a well-nigh hopeless task. These con- 

 torted beds are clearly crushed against a line very slightly trans- 

 gressive upon the D.-anceps zone, which itself everywhere retains the 

 steady strike ard dip of the pale mudstone band immediately above 

 it. It is therefore highly probable that we have here a third line 

 of fault, running generally along the base of the D.-anceps zone. 



That this is actually the case is proved at once upon an examina- 

 tion of the succeeding contorted beds. Everywhere to the north and 

 south of our line of section they show the characteristics of the 

 M. gregarius zone of the Birkhill Shales — the red, blue, and yellow 

 seams of clay, the peculiar lines of nodular concretions, together 

 with swarms of the distinctive fossils, M. gregarius, Rastrites pere- 

 grinus, Diplograpsus tamariscus, &c. 



This fault can be traced from a point near the centre of the upper 



