a re 5s ae ee Sa eel ote at 
Ba 
Burton: Lincolnshire Coast Boulders. 107 
that these had been displaced from the boulder clay 
nti "underlies the san This bed of boulder clay extends 
ver a large area of this part of the country. It underlies all 
the alluvial deposit at the mouth of the Witham and forms 
the bed of a great part of the east side of the Wash. I have 
frequently had to excavate into it, and when constructing the 
uct and outfall works had plenty of opportunity of making its 
acquaintance. It is full of fragments of rocks similar to those 
on the exposed beach at Sutton and Mablethorpe. I gave 
a description of it and of the rocks represented in my ‘ History 
of the Fens,’ p. 456 
‘I quite agree with you in rejecting the theory as to ballast. 
- I am also of opinion that these stones have not come from the 
Holderness coast. There - no drift across the Humber. As to 
the ‘powerful tidal scour’ * suggested by Mr. Harker I do not 
know what this means. The only currents along this coast are 
those due to the tides, about two to three knots, and these 
currents are oscillating, and running for six hours one way 
and as many the other. There is, so far as I know, no regular 
current from N. to S. There is a drift of material along the 
beach from N. to S., but this all takes place landward of the 
point where the waves beat on the beach, and is due to wave 
action and not to currents. This drift collects at Spurn Point.’ 
Now, on referring to the chapter in Mr. Wheeler’s valuable 
work, which he calls attention to, I find the following :— 
‘The base or substratum of nearly the whole of the Fenland 
consists of Oxford and Kimmeridge clay. . . Overlying 
this clay, throughout a considerable area, is a oon known as 
the ‘‘boulder clay.” This is an unstratified mass of lead- 
coloured clay, interspersed with fragments of chalk and lime- 
Stone, and also with basalt, granite, sandstone, and other 
formations quite foreign to this part of the country. Many of 
these pieces of rock are polished and scratched, or striated, in 
a manner peculiar to stones which have been subject to glacial 
action. The following specimens of rocks were found by the 
author amongst the clay excavated for the new outfall of the 
river Witham and for the Boston Dock: red granite with large 
quartz crystals, grey granite, volcanic ash, amygdaloid, felstone, 
felspar, and quartz, porphyry, five different kinds of quartz rock, 
jasper, several different flints, ferruginous and argillaceous sand- 
stones, mountain limestone, dark blue silicious limestone with 
quartz veins, silicious, argillaceous, and carboniferous limestones, 
§reat oolite, iron ore, greensand, chalk; also ammonites of large 
1899. 
