WILMORE : THE STRUCTURE OF SOME CRAVEN LIMESTONES. 169 
The progressive development of this phenomenon may be well 
seen in many new cuttings, the upper part is fossiliferous, the 
lower part apparently very much less so. Similar appear- 
ances may often be seen in the regularly bedded Hmestones 
of the districts where there are no knolls in the restricted 
sense. 
It may be well to recall the evidence for long continued 
drainage in the interior of these knolls, which are so admirably 
situated for the manifestation of its full action — frequent stalag- 
mite deposits, the fluor along the joints (this is not common), 
the pseudomorphs of Liraonite (2 re2033H20) after Pyrites, 
and the occasional grit pebbles found in the underground 
channels. 
It remams to be said that these observations and con- 
clusions refer to the Downham and Clitheroe knoUs in particular, 
and whilst it is quite likely that other knolls in other areas may 
allow of a different explanation, yet I think that at least some 
of these knolls may be thus accounted for. 
I wish in conclusion to express my indebtedness to the 
writings of Prof. Marr and Messrs. Hind and Howe on this sub- 
ject, and especially would I express my obligation to the work 
of Mr. Tiddeman. Whilst venturing to differ from some of 
his conclusions, I am continually feeling in my work in Craven 
how much I owe to his pioneer work in this part of the 
coimtry. 
Bibliography. 
1. R. H. Tiddeman. Report of the British Association, 
1889, page 600, et. seq. 
2. R. H. Tiddeman. Transactions Leeds Geological 
Association, Pt. VI., 1891, p. 112. 
3. R. H. Tiddeman. Excursion Guide (to iVire Valley) 
for the Leeds meeting of British Association, 1890. 
4. R. H. Tiddeman. " On the Formation of Reef-Knolls," 
Geol. Mag., January, 1901, pp. 20-23. 
c 
