ON AN ANCIENT SEA-BEACH. 335 



to cut a trencli into it, thinking to strike the Cliff-beds somewhere behind 

 it, we soon found that the lower part of the section was not the chalk- 

 rubble but a talus slope from that bed covering the blown-sands, and that 

 the thickness of the rubble here was not more than 12 feet. A second 

 trench 80 yards south of our excavation gave similar results, though the 

 base of the chalk-rubble had now sunk to about 6 feet above high-water 

 mark, with a corresponding diminution in the thickness of the blown- 

 sands. It was in this trench that we went through 9 feet of old beach, 

 and reached the solid chalk floor. Seventy yards further south, though 

 the chalk-rubble is still 13 feet thick in the cliff, its base has reached the 

 sea-level, and a short boring was necessary to get below it. This boring 

 showed us that there is here about 4 feet of the bed below high-water 

 mark, and that it rests directly upon a sea-beach of sand with rolled 

 pebbles, the blown-sands having quite disappeared. 



We put down another bore into this bed 30 yards further south, start- 

 ing in the cliff-foot about 2 feet below the top of the bed, and here we bored, 

 into it for 21 feet without reaching its base. The same result followed a 

 boring on the beach GO yards nearer Bridlington, where the upper surface 

 of the bed has sunk below high-water mark and the cliff- foot is held 

 by the overlying boulder clay. .Here we went through 23 feet of chalk- 

 rubble, with sandy and clayey seams fall of water, without reaching its base. 

 One of the clay seams passed through in this boring somewhat resembled 

 a boulder clay in appearance, and, though the samples brought up by the 

 auger were not sufficient for us to decide whether this was indeed a 

 boulder-clay, there are other reasons for thinking that the rubble is partly 

 contemporaneous with the Basement boulder clay, and that there is in 

 places a certain amount of dovetailing between them. 



The Basement Boulder Clay. — The cliff section for half a mile southward 

 from our excavation is nearly always hidden, except just at the top, by a 

 long slope of slipped clay and gravel, and is not often washed by the sea ; 

 but, by a fortunate combination of circumstances, during last March high 

 tides and heavy seas swept the base of this cliff clearer than it has been for 

 ten or fifteen years, and also laid bare a long strip of foreshore stretching 

 at one time or another as far as the sea defences of Bridlington Quay. 

 These exposures enabled the writer to trace the lowest boulder clay of 

 the cliff at Sewerby into the ' Shelly ' or ' Basement ' boulder clay of 

 Bridlington Quay. 



The clay changes considerably in character in this distance, but was 

 traced continuously northward from opposite Sands Cottage, where it is a 

 dark greenish boulder clay of the normal ' Basement ' type, full of shell 

 fragments, to the cliff near our excavation, where it is rather different 

 in colour, is more earthy, has few or no shells and also few boulders, and 

 passes over (and possibly, as already mentioned, partly into) the chalk- 

 rubble just described. As it follows the rise of that bed over the blown- 

 sands to the top of the chalk cliff, it is reduced to a thickness of only 

 8 feet, though there is over 25 feet of it at Bridlington Quay. Above the 

 chalk it may readily be traced along the cliff for two miles to Danes' 

 Dyke, where there is so much splitting up of the beds that it is more 

 difficult to follow ; but there is every reason for believing that it con- 

 tinues beyond, and forms the lowest boulder clay almost everywhere on 

 the headland. Where its base is seen the lowest two or three inches 

 are generally distinctly stratified, with the bedding planes marked by 

 thin films of silty sand ; but, except in a few places, this character dies 



