108 Burton: Lincolnshire Coast Boulders. 
size, some having a diameter of more than a foot. e 
excavation for deepening the upper Witham, some boulders of 
ias li an 
was about 6 feet x 4 feet and 2 feet 6 eee deep, containing 
about 57 cubic feet. 
Many of the fragments of rock found in the boulder clay 
must have travelled very long distances, some from the Nort 
of England and Scotland, whilst some have been recognised as 
belonging to Norway; the rocks being thus pioneers of the 
Scandinavians who followed ave settled here. The surface of 
the underlying strata, on which the boulder clay rests, is very 
uneven, and gives evidence of valleys, river-beds, and other 
depressions having been filled up by it. Large pot-holes, filled - 
with gravel and sand, are frequently met with, and in many 
places this boulder clay rises up above the general level in the 
shape of mounds or hills, as at Sibsey, and at Beacon Hill, near 
Sleaford.’ 
This has a strong bearing on the point; but in a paper 
on ‘The Action of Waves and Tides on the Movement of 
Material on the Sea Coast,’ read by Mr. Wheeler—who is an 
acknowledged authority on the subject—at the late meeting of 
the British Association at Bristol—which paper has since received 
' very favourable mention in the pages of ‘ Nature’—-we find much 
that is more directly applicable to the question, and from this 
paper I must quote at some length :— 
‘Wave action.—With regard to wave action, whether due to. 
winds or tides, Deg aad this is transmitted to the shore from 
the open ocean, the motion is only one of undulation, the 
particles of outee rising and falling vertically, and having no 
forward motion beyond that which they perform in the orbit 
of the wave. i 
shallow water of the shore, and the depth is no longer sufficient 
for the free formation of the undulation, the lower particles 
being retarded by their contact with the shore, and the upper 
particles being also unable to complete their orbital course, are 
projected forward, and the motion becomes horizontal. The 
wave in this condition is capable of carrying forward any 
substance with which it comes in contact, and which is within 
the range of its energy, on to the beach and up its slope.’ 
‘On a flat, sandy shore the water of the breaking wave is. 
distributed over a wider horizontal range, and it comes | 
contact with the beach at a much greater angle than on 
a shingle bank. The force of the impact is therefore less, and — 
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