402 Prof. T. G. Bonney—Tho Chalk Bluf at Trimingham. 



viewed from the nioi-e eastern side, seemed to be prolonged into 

 a slab terminating in a kind of lobe.' The upper part of C and 

 portions of its sloping more western face were also formed of the 

 grey chalk, which Mr. Brj'done found to be generally separated 

 from the white chalk (in which Ostrea Innata is abundant) by 

 a thin seam of ' fine grit ' in which are scattered flint pebbles about 

 the size of a potato, and which "sometimes swells out into 

 a definite bed as much as two inches thick, containing small rolled 

 pieces of Chalk." 



Tins gravel Mr. Brydone assigns to Cretaceous times. He 

 believes that late in that period earth-movements occurred which 

 produced the flexures (attributed by Mr. Eeid to the thrust of an 

 ice-sheet), and that these were followed by denudation which 

 removed part of the chalk and formed the gravelly seam, after 

 which subsidence was renewed and the grey chalk deposited. The 

 presence of water-worn flints in the chalk, as Mr. Brydone remarks, 

 is practicall}' unique, and if his view be correct it would throw "an 

 important light on the time of consolidation of the flints, which 

 must have taken place in this case almost simultaneously with the 

 deposition of the Chalk in which they were formed " (p. 20). It 

 does not, however, appear to occur to him that so unusual an 

 occurrence requires exceptionally strong proof.- 



The infilling of the 'arch' with clay and the apparent passage of 

 the latter beneath the chalk in the masses C and E^ receive from 

 Mr. Brydone the following explanation (p. 77). At some date 

 shortly before the formation of the glacial beds, the chalk must have 

 been again raised and exposed to the erosive action of a sea lying to 

 the south-west of the present coast, the waves of which formed 

 caves in its cliffs, and these caves were filled by the first inflow of 

 boulder-clay. The bottoms of them are probably well below the 

 present beach-level,^ so that we see only horizontal sections through 

 the roofs aud the upper surface of the infilling clay, which then, of 

 course, seems as if it underlay the severed roof by natural deposition. 

 The detached blocks of chalk visible in the cliff behind the ' bluff' 

 " have clearly been carried up by a mass of clay from below, and 

 represent parts of the roofs of these caves which were too weak to 

 resist the upward pressure of the clay." 



I now proceed to give a brief description of what we saw last 

 April. The ' arch ' (Fig. 2) was, more strictly speaking, a big 

 window, the low ' sill ' being formed of the usual boulder-clay, 

 which exhibited a rather marked stratification as it approached the 



' See Plate IX, No. 16, of Mr. Brydone's paper (p. 130). My sketch ended at 

 the sudden rise of the clay, the left-hand one of the two (the oblong block of chalk 

 beyond) being at that time hidden. 



'•* The line of worn tlints between the wliite chalk and the yellowish limestone of 

 Maestricht to the south-west of that town is hardly a parallel. 



^ According to old iliagrams the clay formerly underlay a corner of the chalk of 

 which A is a remnant. 



* If this view be correct, it is a little singular that the chalk should so often show 

 up in this ueighbomhood between tide-marks, still retaining in places a skin of 

 boulder-clay. 



