436 Bristow and Wkitaker — On the Chesil Bank. 



land by a shallow estuary about eigbt miles long, of variable breadtb, 

 but nowhere more than two-thirds and often less than a quarter of a 

 mile wide, which is known as " the Fleet " or '' Backwater" 

 (Plate XV.) ; and for the remaining two miles, nearest to Portland, 

 it has the sea on either side. It is with the last ten miles that we 

 are now chiefly concerned, and to this part the following paragraph 

 refers. 



The average width at the base is 170 yards near Abbotsbury, and 

 200 yards at Portland. The height increases from N.W. to S.E, but 

 the inclination of the crest is not uniform. At Abbotsbury, the 

 crest is over 22 feet, and at Chesil over 42 feet high. Borings made 

 down to l)igh-water level, and sometimes lower, passed through 

 nothing but beach (except at one place, where clay was met with 

 deep down) : ten or fifteen feet from the surface, the shingle was 

 generally mixed with a little sand, and the quantity of the latter 

 increased with the depth until the whole was found to be very com- 

 pact. — (Coode.) 



The largest pebbles are at the eastern end, and gradually decrease 

 in size westward, until near Burton the beach consists of sand 

 and very fine shingle. The accompanying map will make the above 

 description clearer. (See Plate XIV.) 



Westward from the end of the Bank the coast gradually gets 

 higher, and soon there are high cliffs of Liassic, Jurassic, and 

 Cretaceous beds. These cliffs are cut through at Burton and 

 Charmouth by valleys with small streams, such as the Char and 

 the Bredy, which, of course, flow seaward, that is in a south-westerly 

 direction. 



These streams (excepting the Bredy) do not breach the shingle 

 of the bays where they flow into the sea, but turn eastward (the 

 direction of the general set of the current) for a short distance, 

 between the beach and the land, and then filter through the shingle. 

 There is an interval of some miles between each of these successive 

 streams, in which the clifi"s are not breached by valleys, or only by 

 such as are cut off at some height above the sea. On the other 

 hand, along the low shelving shore eastward of Abbotsbury, the 

 least approach to a cliff is a great rarity, and a cliff ten feet high is 

 a marked object : here, therefore, the streams are much closer 

 together, each hollow in the ground sending in its share of water 

 to the still channel of "the Fleet." 



Let us think now what would happen if in former times this 

 latter part had been in the normal state of a beach skirting a low 

 coast. The streamlets flowing down the small valleys would act just 

 as those on the coast to the westward do ; that is to say, they would 

 turn eastward for some distance before filtering through the shingle, 

 and most likely they would run the further between the beach and 

 the mainland, hj reason of the former being so much broader, higher, 

 and more compact than it is on the coast. Now, as the streams are 

 near together, instead of being separated by miles of unbreached 

 cliff, it is quite possible (and we think most likely) that some stream 

 might continue its easterly course between the shingle and the shore, 



