41G MR. s. s. BUCKMAN ois" [vol. Ixxviii, 



sandy deposit (Bridport Sands) onh' by the thin Junction-Bed. 

 This is local stratal repetition. Kon-local stratal repeti- 

 tion is illustrated by the other areas, which show the depositional 

 focus o£ sands travelling northwards into Gloucestershire and then 

 returning southwards to the Dorset coast again. 



In Table III the interval between the Thorncombe Sands and 

 the Bridport Sands seems to be very great, and so it is in the time- 

 scale as well, if the full thickness of deposits made contempomne- 

 ously elsewhere were brought in— 250 feet or so in lilJi-variahilis 

 hemer£e of the Cotteswold Sands alone ; but in actual section on 

 the Dorset coast the break is a very small matter, sometimes or\\y 

 about 2 or 3 feet — so little, indeed, that it may reasonabl}" be 

 inferred that the movements of the Weymouth Anticline have 

 resulted in places in such small upheaval as was necessar}^ to bring 

 about the removal of the Junction-Bed and the superposition of 

 Bridport Sands on Thorncombe Sands in one bed, with a wholly 

 false appearance of sequence. 



In argillaceous deposits stratal repetition is shown in Fuller's 

 Earth, Upper Lias, Lower Lias — to name onh^ a few. And in 

 calcareous rocks the phenomenon occurs — certain strata of especially 

 similar appearance may be named :- — 



Minchinhampton Stone (Great Oolite). 

 NotoTOve Oolite. 



Upper Freestone. I t £ • r\ ^•^. 

 T Ti J. Y Interior Oolite. 



Lower Jbreestone. 



Lower Limestone. J 



These are strata of white freestone with oolitic grains : they are 

 separated by deposits having other characters. 



But to ask for a stratal repetition of a fine-grained white litho- 

 graphic stone of two dates, one Y^Q-fcdciferiim and the other 

 Sammatoceras, to be deposited in the same area so as to form one 

 bed masking a non-secpence of considerable duration, is to make 

 a somewhat extravagant demand, because of the great degree of 

 similarity involved. There are two phenomena to consider — the 

 first is repetition, and the second is coalescence. It wnW greatly 

 strengthen the case to bring forward evidence of the first phe- 

 nomenon in regard to lithographic stone, and of the second in 

 regard to another stone ; because, although the phenomena occur 

 separately, there is obviously only one further step towards finding 

 them occurring together. 



Remarkable confirmation in regard to stratal repetition of a like 

 deposit comes from a neighbouring place, Burton Bradstock ^ ; there 

 is found a white bed (which it will be necessary to discuss presently) 

 of much later date, so similar to the white bed of Watton Cliff 

 that, if portions without their fossils were mixed, separation could 

 doubtfully be made. Now, the greater will include the less. Here 

 is definite evidence that white-stone — lithographic -stone — conditions 



1 I, 5, p. 69. 



