342 
HUGHES : INGLEBOROUGII. 
volcanic outbursts somevvliere not far off. At tlie base tbere is 
sometimes a coarse grit. 
In the Lake District, where this division is well developed, its 
base and its top are still not well defined. Around Ingleborough it 
is not represented at all, unless it may be among the lowest parts of 
the volcanic series of Chapel-le-dale. 
In all such questions of correlation it must be borne in mind that 
volcanic accumulations are from the nature of the case of more limited 
extent than ordinary muddy or sandy sediment, and that among 
them we must expect to find, though we cannot often hope to identify 
with certainty, synchronous beds of very different character in closely 
adjoining areas. This is what Whewell* referred to in his remarks 
upon " Geological Equivalents," and what was further developed 
afterwards under the head of " Ilomotaxis." 
The Bala Series. Volcanic Stage. 
The great masses of green and grey slates, and grits and brecciated 
Conglomerates of Chapel-le-dale, are referred to this horizon from their 
similarity to the Borrowdale beds of the Lake District, and because 
of their constant occurrence below the Calcareous stage of the Bala 
series, the horizon of which is determined by abundant fossil evidence. 
The Bala Series. Calcareous Stage. 
This is the horizon of the beds, the distribution and character of 
which I have been describing in this part of my paper. 
There are three places where the fossils are numerous and well- 
preserved, and the relative position of the beds can be made out — 
1. The stream courses north and east of Horton-in-Ribblesdale 
(see p. .341). 
2. The slope west of Crag Hill up to the base of the Mountain 
Limestone (see p. 339), and, best of all, 
3. The area which lies across the southern end of Crummack 
Dale, between Austwick and Wharfe Gill (see p. 333). 
Other areas have been mentioned above, but in them either the 
exposure is so small or the beds are so crushed that the sequence is 
obscure and the fbssils generally unrecognisable. 
* Op. cit. 
