28 WILMORE : THE STRUCTURE OF SOME CRAVEN LIMESTONES. 
and north-east towards Hellifield. At Gisburn there is a well- 
marked simple anticlina,l — which may be called the northern 
lobe of the system. Exposures on the northern side of this 
anticlinal are very numerous and the dips are tolerably uniform. 
At West Marton and on to Swinden Moor there is a fold 
crossing this system — a synclinal fold or a fault must be hidden 
under the drift at Horton — and this fold has its axis parallel 
to the main Pennine axis, that is, nearly at right angles to the 
general strike of the beds elsewhere. On Swinden Moor and at 
Xappa the continuation of tlie cross-folding systems produces 
a dome-shaped mass with quaquaversal dips. I shall refer to 
these strata again. 
Then there is a long, sharp and well-marked anticlinal — 
the Barnoldswick-Thornton anticlinal — where there is much 
faulting and some overthrusting, with strikes on the whole 
steadily S.W. to X.E. 
It is not too much to say that in nearly every one of the 
very numerous exposures in this Barnoldswick-Thornton massif, 
either faulting or folding of the beds may be seen, with abundant 
slickensiding (see Plate I., Fig. 2, and Plates III. and IV.). 
These beds will also be mentioned again. 
Lastly there is another dome-like mass between Broughton 
and Gargrave, very much like the Marton-Swinden mass already 
mentioned. I have not included much of this mass in my 
work. 
Thus while the domina,nt folding strikes S.W.-X.E., there 
is also folding nearly at right angles to that direction, just as 
is seen in the neighbouring Coal-field of Burnley. The cross- 
ing of these folds is of considerable significance in explaining 
the structure of the district. 
The literature is already considerable. 
The district is described in the Survey Memoir on the Burnley 
Coal-field. (Of course Phillips included it in his Geology of 
the Limestone District of Yorkshire.) Mr. Tiddeman has 
made several communications to the British Association Reports 
and other literature respecting the Reef-knolls in this and ad- 
jacent areas. Prof. Marr (Q.J.G.S., Vol. Iv., 1899, 327-361) 
disputed Mr. Tiddeman's theory of Reef-knolls and proposed 
