Geology 



In the limestone bed were fragments of trilobites, 

 one of which appeared to belong to the genus Stauro- 

 cephalus, while another was certainly a Calymene, and 

 from this we judged that we were dealing with rocks 

 of Silurian age. 



The dips of the Carboniferous Limestone and of 

 these Silurian beds were so discordant as to preclude 

 the idea of a conformable junction, and as a whole 

 formation, the Devonian, which should lie between the 

 Silurian and Carboniferous, appeared to be absent, it 

 was clear we must be dealing with either a fault or 

 a great unconformity. The direction of dip of the 

 Carboniferous favoured the former, but it would be well 

 to seek direct evidence before coming to a definite 

 conclusion on the point. 



With this object in view we followed the boundary 

 line, and presently reached a low, brown, heath-covered 

 hill, surrounded on all sides by limestone clints. In- 

 vestigation proved this to consist of " Millstone Grit," 

 and the junction with the underlying Carboniferous 

 Limestone was clearly conformable. 



The grit could be traced to within 50 yards of an 

 exposure of the gray shales, the intervening country 

 being occupied by Carboniferous Limestone. 



It now became clear that there was no room in the 

 section for the Carboniferous Limestone which we knew 

 to be at least 600 feet in thickness in this district, so that 

 we were again driven to the conclusion that the junction 

 was a faulted one, and that the throw of the fault was at 

 least 600 feet. 



A north-east to south-west section through the hill 

 would thus be shown in Fig. 24. This fault, which 



152 



