394 G. W. Lamp'lugh — The Boulder-clay at Bridlington. 



Above the " Basement " clay, there sometimes lies a snuff-coloured 

 clay, which is generally beautifully laminated. This clay is abso- 

 lutely destitute of pebbles, and contains no shells, nor, in fact, any 

 foreign admixture. Its thickness is very variable, but it does not 

 often exceed four or five feet. 



In the exposure at Eeighton just referred to, I saw patches of this 

 clay occupying the same position with regard to the Boulder-clays 

 as at Bridlington. 



One feature of great interest, which I have lately seen in connexion 

 with this clay, is that, in some places, it shows a very well-marked 

 unconformity between its upper and lower parts. 



The lower division, which is the thicker, consists of very fine, pure 

 clay, clearly laminated, but twisted and contorted in all directions. 

 Over it lies the upper division, which is more sandy in nature, and 

 is also finely laminated, but lies perfectly even and undisturbed 

 over the edges of the contorted laminge below. This upper part 

 also occasionally shows clear steep ripple-marks, running E.N.E. 

 by W.S.W., and having their steep sides facing S.S.E., which 

 shows the probable course of the current by which they were 

 formed, to have been from the N.N.W. 



In one or two places a seam of sand comes between this Laminated 

 clay and the overlying Boulder-clay (see Section, E.). 



Besting generally on the Middle Laminated clay just described, 

 but where that bed is absent, directly on the " Basement," is another 

 Boulder-clay, known as the " Purple" clay. It contains a few well- 

 worn and rounded shell-fragments. It has, also, numerous inter- 

 calated beds of sand and gravel, which contain no shells, and which 

 do not generally continue for any distance. To this, however, there 

 is an exception in the case of the bed D of the section, which may 

 be traced continuously northward for over half a mile, when it is 

 lost to sight amid the slips which there obscure the cliff. 



A slight difference is observable between the clay above and below 

 this sand bed. Both the sand, D, and the upper bed of Boulder-clay, 

 C, swell out to a much greater thickness a little further to the north 

 of the section, the sand attaining a thickness of 12 feet, and the clay 

 of nearly 10 feet. It is a matter of conjecture whether this upper 

 band of clay may not be a continuation of the peculiar clay, presently 

 to be referred to as covering the freshwater remains, a point which 

 can hardly be satisfactorily settled, as the sand and gravel bed, D, 

 dies out 70 yards north of the position of the freshwater remains on 

 the beach, and these latter also are only seen in a horizontal exposure, 

 and not in section. But if the band of clay, C, is really separate 

 from the remainder of the Purple clay, it may of course be continued 

 after the sand and gravel bed has thinned out, and resting then 

 directly on the Purple clay ; in which case, as the difference between 

 them is only slight, it would be difficult to mark the line of division. 

 There is certainly a difference between the upper and lower portions 

 of the mass of clay, which forms the base of the cliff just under 

 Sands Cottage, the upper part being more stony, and showing irre- 

 gular streaks of various tints, generally greenish. 



