M. M. Bryclone — Further Notes on the Trimmingham Chalk. 21 



for the three upper lines of flint shown in fig. 1 of my previous 

 pamphlet ran steadily and strongly up to the grit seam at the base 

 of the grey chalk, and were then cut off by it. A fairly accurate 

 representation of this state of things can be got by adding to the 

 last-mentioned figure two feet of chalk resting horizontally on the 

 truncated ends of the lines of flint. As the bluff was cut back these 

 lines of flint sank, and after a time the lowest came wholly below 

 the base of the grey chalk and formed a perfect arch. 



2. The Fissure and its immediate surroundings. 



The triangular mass of clay filling the fissure was denuded much 

 more rapidly than the chalk, and soon there was produced a definite 

 inlet between two faces of chalk, which gave partial cross-sections 

 of the masses of chalk. It became almost at once apparent that the 

 grey chalk was really only a thin coating (thicker at the top and 

 bottom on the slope than in the middle, but nowhere more than 

 18 inches thick) of a sloping surface of 0. lunata chalk. The filling 

 of the gap by clay proved in places to be incomplete, so that 

 a considerable space was left between the top of the clay and the 

 chalk arch, indicating that the clay was either very slightly fluid 

 or not under great pressure when forced in. The latter cause seems 

 the more probable, as if there had been great pressure at this point it 

 is hardly possible that an arch of chalk, with a maximum thickness 

 of two feet, should have remained unbroken. The grey chalk soon 

 appeared in the arch forming the upper part of it in a gradually 

 increasing proportion and connecting the grey chalk on the bluff 

 with that on the ' slope,' but it never completely cut out the 

 0. lunata chalk which still formed the lower six inches or so when 

 it was destroyed by the waves. About two-thirds of the way up the 

 slope, was one of the points where the grit seam swelled out into 

 a regular bed with pebbles and rolled chalk. 



3. The Bay of Grey Chalk. 



The first event was the removal of the talus at the head of the bay 

 and the exposure of a continuous surface of grey chalk beneath it. 

 Then the grey chalk became thinner and finally disappeared altogether, 

 both at the head of the bay and along the median (horizontal) line 

 of the ' slope.' But while in the latter case the underlying stratum 

 was 0. lunata chalk, as might be expected, in the former case it 

 proved to be clay similar to that at the back of the bluff. Further 

 denudation of the grey clay exposed at a number of points 0. lunata 

 chalk coming in between the grey chalk and the clay as the edge of 

 the grey chalk shrank back from the cliff (PI. IV, Fig. 9) . 



4. The Bay on the South of the Muff. 



This is but poorly shown in our PI. II, Fig. 2, which was taken 

 at a time when there was no particular feature of interest in the 

 south bay. It only offered a section through the bluff and a mass 



