Dr. A. Wilmore—The Northern Pennines. 547 
moisture of the burrow causing the grains to adhere and dry in 
a crescent-shaped form around the margins. After the surface- 
markings have dried and slightly hardened, dry dust or sand must 
blow over them before a fresh tidal deposit flows over and entombs 
them to form a problem for some future geologist to puzzle over.— 
Ep. Gon. Mace. | 
EXPLANATION OF PLATE XIII. 
Fie. 1la.—Circular impressions developed on the surface of water-laid sediment 
by vertical currents. 
16.—Part of the same surface seen in Fig. la, rather more enlarged. 
2.—Photograph of part of a slab from the Bay of Fundy (see supra, p. 546). 
29 
99 
I1V.—A Sxercu oF THE SrrRucrure oF THE NorrHeRN Pennines.! 
By Dr. A. WILMORE, F.G.S. 
f{\HIS paper attempts a brief summary of the structure of the 
Northern Pennines for geologists and geographers, especially 
for those who are interested in the relation of geographical form to 
geological structure. It is, for the most part, a re-statement, and 
advances little that is new; but it is thought that the present visit 
of the Association to the North may be a fitting opportunity to 
summarize our knowledge of the structure of an interesting region, 
especially as considerable progress has been made in our detailed 
knowledge of the Northern Pennines since the visit of the Association 
to Newcastle in 1889. 
By the ‘‘ Northern Pennines” as treated in this paper, we mean 
that well-defined part between the two great gaps—the Tyne Gap 
and the Craven or Aire Gap. Im this part of the Pennines the 
mountain masses are broader and higher, and the structure is some- 
what different from that of the Pennines south of the Craven Gap. 
The familiar anticline is not so conspicuously developed as in the 
southern half of the Pennines. 
In the Northern Pennines the student may see very clearly indeed 
the broad dependence of the topography upon rock-character, rock- 
position, and geological history. 
The Craven or Aire Gap may be taken as a convenient starting- 
point. This is a lowland region of roughly triangular form drained 
by four local river systems: the Wharfe, the Aire with Broughton 
Beck, the Ribble with the Lancashire Calder, and the Wenning (one 
of the feeders of the Lune). Each of these outlets of the ‘gap’ is 
utilized by a railway. The Leeds and Liverpool Canal follows the 
valleys of the Lancashire Calder and the Aire, and crosses the 
Pennines at an elevation of a little over 500 feet (the highest point 
is at Foulbridge Tunnel, near Colne). 
The Middle Pennine Gap is determined by the great Craven Fault 
system and the folding of the strata to the south and south-west of 
~ the fault. The general direction of the folding is from W.S.W. to 
1 Read before the British Association, Section C (Geology), Newcastle, 1916. 
