crofts: notes on ALEXANDRA DOCK EXTENSION, HULL. 247 
known as the "purple" or the "basement," but as there is 
considerable difficulty in differentiating these clays, in the absence 
of shells or other undoubted feature, in so favourable a situation 
for observation as the cliffs of the Holderness coast, it is not 
advisable to be too definite here. 
The gravels overlying the lowermost boulder clay are composed 
of rocks of similar character to the boulders in the clay, sometimes 
rounded, sometimes angular, often striated and of distinctly glacial 
origin, and at the southern end, particularly where most developed, 
stratified and divided into thin beds by bands of clay, silt, sand, 
ttc. These beds dip about 6" south by east, and at the southern 
end are capped b}' the lower shell bed. Towards the north the 
bedding, of the gravel becomes more regular, the constituent 
particles finer and more compact, and the upper portion gradually 
passes through bedded sand into a red stoneless clay. Nearer 
the northern end of the trench the glacial beds above the lower 
boulder clay are as follows : — 
ft. 
in. 
Ked clay 
5 
0 
Gravel 
3 
6 
Stiff grey chalky boulder clay 
4 
0 
Grey stoneless clay 
0 
9 
Purple stoneless clay ... 
0 
9 
Rippled sandy clay 
2 
0 
Stratified sand ... 
2 
0 
The sand is bedded and passes upwards into an interesting 
rippled sandy clay with carbonaceous markings in the ripples. 
The ripples are about 10 in., crest to crest, the trough between 
them being about 2J in. deep, the axes being about N.N.E. ; 
the incidence of each overlying crest is not perfect, the 
deposition of each group of layers developing on the eastern side 
of the crest, the large number of layers forming each group 
point to a considerable amount of time being occupied by their 
deposition. This bed gradually passes upwards, the junction not 
being of a definite character, into the fine purple stoneless clay, 
followed by a bed of similar clay and thickness, but of a grev 
L 
