B. M. Brydone — Further Notes on the Trimmingham Chalk. 125 



one fault. The section attached to the ridge coated with a sheet of 

 flint is a good second in size, showing chalk in regular sequence for 

 a length of over 400 yards, and maximum (exposed) breadth of 

 about 45 yards. 



There seem to be only two possible theories as to the nature 

 of these chalk masses, as Mr. Eeid's theory is quite impossible of 

 general application, and appears to be only applicable to the north 

 bluff subject to very important modifications. One is the erratic 

 theory. This theory involves the possibility of an erratic 1,000 

 yards by 200 yards in superficial area and unknown depth, and 

 others smaller but still of monstrous size. It offers no explanation 

 of the rude symmetry of tectonic structure exhibited by the chalk, 

 nor any plausible origin for these erractics, which have no known 

 counterpart in fossil contents, and cannot from the perfection in 

 which they have retained their stratification and fossil contents have 

 travelled far. It is also a coincidence almost past belief, until every 

 other possible explanation has failed, that an ice-sheet should chance 

 to leave at one spot all the known remnants (a very large number) 

 of a very strongly marked epoch without the admixture of a single 

 erratic mass belonging to any other epoch. If a final nail in the 

 cofiin of the erratic theory be required, it is to be found in the 

 Mundesley well section recorded in the Geological Survey Memoir 

 on the Upper Chalk of England as having shown a great thickness 

 of chalk, obviously in situ, containing 0. lunata at intervals. 



The other theory is that of the buried chalk cliff, set forth in my 

 previous pamphlet (of which Mr. Jukes-Browne's buried sea stacks 

 are really a variant very near the truth, but not quite borne out by 

 my investigations). The numerous sections on the foreshore where 

 the clay is piled up against apparently vertical faces of chalk, the 

 uniformity with which the clay has hitherto been found to be 

 bounded to seaward by chalk, the occasional disturbances in the 

 chalk along its junction with the clay never penetrating more than 

 a short distance into the body of the chalk, the newly exposed 

 cavities in the southern part of the south bluff, and the great 

 masses of flint shingle in the cliffs immediately above the 

 bluffs, all tend strongly to confirm the supposition that the chalk 

 once presented at this point a low cliff with projecting headlands to 

 a sea lying where now we have the land, and that up against this 

 cliff the boulder-clay was piled. It is not at all uncommon to find 

 the chalk much disturbed along the junction with the clay, while 

 a few yards further seawards there commences an extensive 

 area of wholly undisturbed chalk, and this is no doubt due to the 

 dislocation of the chalk in the face of the old cliff by clay forced into 

 cracks and acting under continued pressure from behind like 

 a gigantic wedge. The erratics behind the north bluff have almost 

 demonstrably been torn from the parent mass by clay pressing up 

 from below, which must have reached a position below them either 

 in caves or along cracks. 



There are, as will have been gathered, many apparent instances on 

 the foreshore of clay passing under the chalk. Some of these are 



