PHYSICAL CONDITIOXS EXISTING FEOM START POINT TO PORTLAND. 529 



relations between tides and bottom-soil they, of course, give no account, 

 and it is with these the present paper will deal. 



In the various pilot guides to the English Channel a great amount 

 of information is given with regard to the tides in the different regions, 

 and much light is thrown on the circulation of the water within the 

 line from Start Point to Portland and its relation to the tides at the 

 mouth of the Channel ; but here, again, the inshore currents are barely 

 mentioned, and the relation of the currents generally to the formation 

 and changes of the bottom-soil not at all. 



Several papers contributed by Mr. H. N. Dickson to this Journal 

 (vol. ii.) deal with the distribution of surface temperatures in the 

 English Channel. Comparatively few records were taken within the 

 area here considered, but during the summer of 1891 it was found that 

 in Start Bay,* so called, a warm upper stratum of water was super- 

 posed upon a cold lower layer nearer the bottom. In other respects 

 than temperature the two strata were alike. Special emphasis was 

 laid by Dickson upon this discovery, even though observations made 

 in the succeeding winter failed to corroborate it. It showed that the 

 colder waters from west of the Start were able to penetrate under the 

 almost stagnant upper layers within the Great "West Bay. 



With regard to the action of waves and currents on the shore a 

 great deal of literature exists, but it is unnecessary to enter into this 

 aspect in any detail. Eeference need only be made to the paper of 

 Vaughan Cornish on the famous Chesil Beach near Portland, and to 

 the recent work of "Wheeler on the Sea Coast : Its Destruction and 

 Protection. In the former the much -disputed origin of the Chesil 

 Beach is discussed, and a theory stated which seems to accord well 

 with the phenomena observed. As will be shown later, this theory is 

 accepted here and applied to phenomena very similar, though on a 

 smaller scale, at the other extreme of the area, namely, Slapton Sands 

 in Start Bay. In the latter work an interesting account is given of 

 the actual condition of the shores and the littoral drift on the south 

 coast. Eeference will be made to it later. 



The Great "West Bay is 48 miles across from Start Point to Port- 

 land, and extends 20 miles inwards. Its area is about 650 square miles. 

 It opens to the south-west, so that its easterly arm towards Portland 



* Considerable doubt exists as to the right name to apply to the region within the 

 line from Start Point to Portland. Dickson refers to it as Start Bay, but this is 

 obviously incorrect. Wheeler calls it Lyme Bay, but Lyme Bay is more usually restricted 

 to the northern portion from Hope's Nose or Straight Point to Portland. It seems advis- 

 able to have a distinct name, however, because Start Point and Portland form the natural 

 boundaries to a compact series of phenomena, and the name Great West Bay, used by 

 Mr. A. R. Hunt (The Evidence of the Skerries Shoal on the Wearing of Fine Sand by 

 Waves, 1897), has been adopted in this paper. 



