356 
HUGHES : INGLEBOROUGH. 
conditions has affected also the Carboniferous rocks, but of 
that anon. Thus we have in the Bala series and in the 
Silurian a southern and a northern type, according as the 
deposits were laid down on the south or on the north of the 
great Mid- Wales axis of earth movement which I have described 
above. 
The Silurian of Ingleborough belongs to the northern type. 
It is also interesting as being the most easterly exposure, in the 
north, of rocks of this age, and it may therefore be useful to 
give a table (p. 360) pointing out as nearly as ma.y be its place in 
the series with its sub-divisions and their equivalents elsewhere. 
When the palseontological vernier is applied the general sequence 
suggested by the succession of beds of different lithological 
character is well supported. But first of all let us set forth 
that which can be easily verified, that which can be mapped, 
that which will enable a student to fix and record the exact 
horizon in which he may find certain fossils. 
As we follow the Bala Beds upw^ards in ascending section 
above the Coniston limestone and shale, many stratigraphical 
and pal^ijontclogical difficulties present themselves. We find 
that there must have been some change in the conditions which 
affected the character of the sediment and favoured the incoming 
of new forms of life into this area. The fine mud of Ashgill in 
the Lake District and of Fairy Gill, and many another little 
known stream north of Ingleborough, was then laid down. This 
"Ashgill Shale," wherever it has been detected, is in conformable 
succession to, and is bracketed with, the Bala Beds. It has not, 
however, been recognised everyAvhere at the top of the Bala Beds, 
and it varies in thickness, but we have not yet sufficient data 
to infer with any confidence whether this is due to original un- 
equal or irregular deposition or to a small unconformity at the 
base of the Silurian. 
The Ashgill Shale is not well developed anywhere under 
Ingleborough. I did not see anything that I could refer to it 
at Crag Hill, but it may be detected yet on the lower slopes. 
The rock immediately beneath the basement bed of the Silurian 
at Austwick Beck Head is so crushed that recognisable fossils 
are not likely to be found in it. but there also it would be worth 
