232 MK. H. H. Ar.NOLD-EEMKOSE OX THE GEOLOGY OF [May 1 899, 



continued and lies between the quarry and the Mountain Limestone 

 in the Crake Low cutting, though I have not been able yet to find 

 it in situ on the slope of the hill. On the eastern side of the line 

 the ash can be traced only for a short distance from the Highway 

 Close Barn cutting, because the limestones above it dip rapidly down 

 towards the east and cover it up. 



The rocks through which the Highway Close Barn and Crake Low 

 cuttings have been made form on the whole a long narrow dome, 

 with minor basins in it, through the long axis of which the railway 

 runs. Eig. 1, p. 230, gives a section across the railway, seen in the 

 limestones above the ash at the northern end of Crake Low cutting, 

 before the rocks were cut through. 



Fig. 2 (p. 230) is a similar section across the northern end of 

 Highway Close Barn cutting in the shales and limestones above the 

 ash, and fig. 3 (p. 230) a section across the same cutting at the 

 southern end. This dome brings up the small inlier of Mountain 

 Limestone seen in Crake Low cutting. 



The tufaceous limestone and shales in the Highway Close Barn 

 cutting are apparently carried up by the dip to Crake Low Quarry, 

 and then brought down by the fault which passes near the farm of 

 the same name. It would seem, therefore, that the deposits of ash 

 in the two cuttings, which are the third and fourth exposures of ash, 

 belong to the same bed. I have shown that the two beds of ash in 

 the Tissington cutting, which are the first and second exposures, are 

 really one bed, and so far as the evidence obtained by mapping 

 goes, it points to the conclusion that the second and third exposures 

 are also of the same bed. We are, therefore, compelled to conclude 

 that there is only one thick deposit of ash in the three cuttings, 

 succeeded by limestones and shales with intercalations of tufi". 



A comparison of the vertical sections (PI. XYIII) shows a difi'erence 

 ill the beds above the ash in the three cuttings. The limestones 

 become thicker, and the shales decrease as one goes northward from 

 sections 1 to 5 ; in one place shale and thin limestones have been 

 deposited above the thick ash, and in another numerous beds of lime- 

 stone with thin shale-partings : in the former is a preponderance 

 of shallow- water deposits, and in the latter a preponderance of rocks 

 formed in deeper water. If my contention that only one thick ash- 

 bed is present be correct, there was deposited immediately after the 

 great outburst in one place what would be called Lower Yoredale 

 Beds and what were mapped as such by the ofiicers of the Geological 

 Survey ; and in another place, not far distant, what are lithologically 

 more like the upper beds of the Mountain Limestone Series and 

 have been mapped as such by the ofiicers of the Survey. These beds, 

 though totally unlike in character and apparently belonging to 

 diff*erent series, are really of the same age. 



In only one place is the ash-bed exposed to view from top to 

 bottom, namely, in the middle of the Tissington cutting. Here 

 it is about 144 feet thick. In the three other places in which it 

 appears, only the upper portions are seen ; a thickness of about 



