DAKYNS : GLACIAL PHENOMENA OF WHARFEDALE. 
305 
I believe that the true explanation is this : At the foot of 
Kilnsey Crag strong springs break over from the limestone rock, just 
above the level of the alluvium ; and also in Littondale strong 
springs break out at the foot of the limestone scars, the hillside 
below being formed of a mass of detritus, which as completely con- 
ceals the underlying rocks as the alluvium at Kilnsey does, Now, 
seeing that strong springs break out at the foot of scars formed by 
limestone of great thickness, and that it is only a little way below 
the springs that we find Silurian boulders in the dale, it seems likely 
that the springs are thrown out by Silurian rocks in places in the 
bottom of the valley, hidden from sight by superficial detritus, drift 
and alluvium, and that our boulders were thence derived. This 
makes everything simple ; and the thickness it allows to the lime- 
stone is quite equal to the thickness of the limestone in Ribblesdale. 
In conclusion let me say that thus far the drift phenomena of 
Wharfedale lend no support to the theory that the whole country 
was once overridden by an ice cap descending from the pole. There 
is no evidence here of foreign ice ; but everything is in favour of 
huge confluent glaciers, or ice-sheets if j r ou like, of home-made ice. 
Nidderdale, too, supports the same conclusion. There are no 
foreigners there at all. 
