122 



A. J. JUKES -BR0W2fE ON THE 



white Chalky Clay of the high lands that its separation therefrom 

 ought not to be a difficult task if it maiatains its usual characters ; 

 but it is conceivable that if newer than, and banked against, the 

 Chalky Clay the reconstructed material of the latter would give it 

 a different aspect and introduce a source of confusion and diffi- 

 culty. 



If the Boulder-clay which borders the western side of the Fenland 

 is distinct from, and newer than, the bluish-grey clay which occurs 

 on the southern borders, and if both pass beneath the Pens, then 

 the newer clay ought to be found overlying the older clay in the 

 neighbourhood of Boston. The large excavations made for the new 

 docks at Boston last year enabled me to test this expectation. The 

 section I found at the bottom of the dock-basin in I^ovember was : — 



Clay and silt 18 



Peat 1 



White and grey sands 1 



Reddish sand and stones in pockets worn in mottled buff 



and grey Boulder-clay about 6 



The Boulder-clay with the reddish sand and gravel in pipes 

 and pockets was similar in appearance to that near the western 

 border of the Fen, just, in fact, such as the surface near Heckington 

 and Hale would present if now submerged and covered by newer 

 deposits. In a deeper trench, between the dock and the river, a 

 dark-blue Boulder-clay was exposed underneath the mottled clay 

 which forms the base of ths dock-section. The line of junction was 

 not clear, but appeared to be a sharp one. 



The existence of so-called Hessle Clay beneath Boston, anticipated 

 by me in 1879 *, is thus confirmed, though its thickness is but small. 

 The upper portion has probably been carried away by erosion, so 

 that only the basement part remains. 



My reason for suspecting the existence of this clay beneath 

 Boston was that it occurs in the form of an island at the sui-face 

 near Sibsey, about five miles to the IS'.IS'.E. ■ Here and at Stickney, 

 still further north, the clay is of a uniform purple-brown colour, 

 this being apparently the tint of the upper portion of the " brown- 

 clay series " in the Fen district f. 



From Stickney this clay continues by Stickford to the northern 

 border of the Fenland, of which it forms the margin by Keal Coates, 

 Toyuton, and Little Steeping to Firsby, where we commenced this 

 description of its range. This ground was described in the paper 

 already referred to ; but there is one point to which I desire to recall 

 attention : this is the existence of sand-banks along the northern 

 edge of the Boulder-clay tract, where it is banked up against the 

 slope of the Kimmeridge Clay. This bank forms a kind of terrace 

 at the foot of these hills, and appears to indicate a shore-line. This 

 is of the greater importance, because the original margin of the 



* Quart. Journ. Greol. Soc. vol. xxxv. p, 420. 

 t These clays may therefore belong to the Purple and not to the Hessle Clay. 



V 



