350 SECTIONAL TRANSACTIONS.— E. 



To the natural excellence of the estuary was due the fact that little artificia 

 improvement was carried out till near the end of the century, while the very heavy 

 programme of dredging which has given 30' L.W.S.T. up to Purfleet, 27' to the middle 

 series of docks, and 20' to the Surrey dock, has all been carried out in the last twenty 

 years under the energetic control of the P.L.A. The very considerable tidal range 

 gives, of course, much greater depth than these for most of each tide. 



The points of critical limiting depth in the early and middle century were shown 

 by examples from early charts. The position of the legal quays, the cartage distance 

 of wharfs from the city, the convenient distance at which a lighter could work (always 

 on the tide) between vessel and wharf ; all these were factors in the crowding of the 

 Pools in the earlier part of the century. 



The physical conditions favoured loading from and into lighters, and so important 

 became the river wharfinger and lighterage interests, that a ' free lighter ' clause was 

 introduced into the whole series of Thames Dock Acts ; and in the docks to-day much 

 of the loading and unloading is done by lighters. 



With the coming of big steamers in the 80"s and 90's, shoals below Gravesend in 

 the Lower Hope and in the Sea Reach, began to give trouble. These have been 

 successfully dealt with, and the channel is largely self-maintaining. 



Diagrams were shown illustrating the changes in the outer estuary, below the 

 limit of dredging, for the period from 1812 to the present day. Some of the swatchways 

 appeared to be compensatory in character, the decay of one accompanying the forming 

 of another. 



Brief allusion was made to the major new works which were keeping the port of 

 London abreast of the times, viz., the enlargement of the entrance of the older docks, 

 the splendid George V. dock, and the quite new entrance lock, dry dock and landing 

 stage at Tilbury. 



Dr. S. W. WooLDRiDGE and Mr. D. J. Smetham. — The Geographical 

 Features of the Boulder Clay Margin in Essex and Hertfordshire. 



The limit of the Boulder Clay and its associated gravels in both Essex and Hertford- 

 shire coincides with a marked change in every aspect of the geography of the country. 

 The Boulder Clay area shows a general unity in its features of morphologj', drainage, 

 soil, vegetation and surface utilisation. In Essex these features are sharply contrasted 

 with those of the London Clay country with its broad low-lying stretches of drift-free 

 pasture land diversified by scattered remnants of a dissected high level plateau 

 retaining a capping of sand and gravel. The contrast is clearly reflected in the 

 historical geography and agricultural development of the area. 



An equally striking contrast which, however, involves somewhat different factors 

 occurs in Hertfordshire where the Boulder Clay country gives place abruptly to the 

 Chalk plateau. Particular attention will be drawn to the well-marked geographical 

 characteristics of the Vale of St. Albans where the glacial deposits project westward in 

 a clearly defined strip between the Eocene escarpment and the base of the Chiltern 

 dip-slope and where their influence upon settlement and agriculture is of especial 

 interest. 



An important and unrecorded feature of the area as a whole is the widespread 

 occurrence of loams essentially identical with true loess which have exercised consider- 

 able control on the agriculture and which may be regarded as marking the continuation 

 of the loess belt of continental Europe into southern Britain. 



Mr. H. J. Wood. — Agricultural Distributions in Scotland. (With exhibition 

 of maps.) 



With a view to compiling an agricultural atlas of Scotland a series of maps, 

 on a scale of eight miles to the inch, have been constructed to show agricultural 

 distributions on a dot basis. Two base maps were necessarj', one of parishes, 

 and the other to show the extent of the uncultivated area, i.e. moorland, loch and forest. 

 The latter was based on the inch Ordnance Survey maps of Scotland, black outline 

 edition. These maps together served as a basis for plotting the agricultural statistics 

 generously furnished by the Scottish Department of Agriculture and relating to 1927, 

 a normal year. 



By wa^' of introduction four sets of graphs were drawn to show the main historical 

 features of agriculture north of the Border, and to provide a setting for the year 1927. 



