46 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Juiie 14, 



seeds of plants amongst the mass of fragmentary vegetable remains 

 in the septaria. 



The cliffs range westward about half a mile without any lower 

 strata outcropping. For a distance of nearly a mile we then find 

 nothing but low cliffs of sand and gravel, which interrupts the se- 

 quence of stratification. When the cliff rises again it consists of 

 gravel underlaid by whitish and yellow sands regularly stratified, but 

 with no characters sufficiently definite to indicate to what exact part 

 of the series they belong. After a continuation, however, of this 

 section for about half a mile, we luckily meet with a slight throw-in 

 of an overlying stratum, which enables us to resume the plan of super- 

 position in descending order. The section is as follows. 



Fig. 3. 



Ochreous flint gravel. 



a. Dark grey clay mixed with 



patches of greensand. 



^g^ b. Rounded flint pebbles in whi- 



^^^= tish sand. 



^^ c. Sands — white and yellow. 



Here we evidently have in a small depression the base of the 

 Barton clays. The peculiar appearance of the clays "a" and of the 

 bed of pebbles " h " cannot, at this short distance from its last ap- 

 pearance, be mistaken, and this structure and order is peculiar to this 

 part of the series. 



After this slight reappearance the Barton clays are not seen again. 

 As we proceed westward the cliffs rise in height, and range uninter- 

 ruptedly to the entrance of Poole Harbour, a distance of six miles 

 and a half; but, as observed by Sir Charles Lyell, the section is 

 continued " so precisely in the line of bearing of the strata that no 

 new beds rise up ;" the whole consisting of the sands which imme- 

 diately underlie the Barton clays. 



Notwithstanding, however, the want of fresh outcrops, there is 

 much to interest in the illustration which these strata afford of rapid 

 changes of condition within short distances. 



To commence with the pebble bed " &." This at first sight might 

 appear to thin out, whereas it in reality forms the upper part of the 

 cliff for a considerable distance westward ; but, from the circumstance 

 of its immediately underlying the common surface-gravel in this part 

 of its course, it may readily be confounded with it ; a closer exami- 

 nation will, however, distinctly show the difference between the two. 

 The one is a confused mass of angular, with a few round, flint pebbles 

 in clayey ochreous sand ; the other consists uniformly and solely of 

 perfectly rounded smaller or larger flint pebbles, mixed with more or 

 less sand, and always, when the latter predominates, showing distinct 

 though rough stratification. 



At Alum Bay we have seen this bed of pebbles about six inches 

 thick (see Section of Alum Bay, stratum 28), and consisting of pebbles 

 about the size of an egg. 



At the end of Barton Cliff the pebbles are generally larger, and 

 the bed is about a foot and a half thick. At Hengistbury Head its 



