The Melbourn Bock and the Zone of Belemnitella plena. 283 



3. " The Thames Valley Surface-deposits of the Ealing District 

 and their associated Palaeolithic Floors." By John Allen Brown, Esq. 



The author stated that his paper might be regarded as in some 

 degree supplementary to that by Colonel Lane-Eox, published in 

 the Quarterly Journal of the Society in November 1872. He re- 

 ferred to Mr. Whitaker's division of the Thames-valley deposits 

 into three terraces, namely : — 1. The lowest now seen in bends of 

 the river, 10-20 feet above 0. D. ; 2. The middle terrace, 20-40 

 feet ; and 3. The high-terrace gravel, 50-100 feet, extending up to 

 the shoulders of the hills, and, according to the author, much 

 higher. The high-terrace gravels near Ealing reach nearly to the 

 top of the hills forming the inner valley-ridge, the highest point 

 in which is the Mount at Ealing, 204 feet. The summit of this, 

 when excavated for a reservoir, was found to be occupied by 

 thick beds of gravel of different character from the valley- 

 gravels, and not of fluviatile or estuarine formation ; the same gravel 

 occurs upon other elevations, and patches of it, appearing here and 

 there, show that it probably once extended right along the ridge and 

 over Hanger Hill. Similar materials to those forming this gravel 

 also occur scattered over the surface of the ground. On the Mount 

 these gravels filled a series of furrows or channels, beneath which 

 were horizontally stratified deposits of white sand, loam, and loamy 

 clay, which were pressed out of the line of deposit where the jagged 

 furrows occurred ; and from all the characters presented the author 

 inferred that these deposits were due to the action of ice which had 

 stranded and melted here, and deposited its burthen of glacial 

 detritus. The author described the deposits of gravels, brick-earth, 

 &c. at various points in the district, and noticed that the high- 

 terrace gravels between 60 and 125 feet contain seams of black 

 matter, apparently due to the decay of vegetable substances, which 

 recur at more or less regular intervals, and serve to indicate three 

 or four lines of old land-surfaces. In connection with these land- 

 surfaces, especially in some pits excavated in the Creffield Boad, 

 about 100 feet above O. D., numerous worked flints were found, the 

 characters and mode of association of which led the author to think 

 that we have here traces of a regular manufactory of flint imple- 

 ments. He further indicated the conditions under which he con- 

 sidered their preservation in this locality had taken place. 



February 10.— Prof. T. G. Bonney, D.Sc, LL.D., F.B.S., President, 

 in the Chair. 

 The following communications were read : — 



1. "On anew species of Psilotites from the Lanarkshire Coal- 

 field." By B. Kidston, Esq., F.G.S. 



2. " The Melbourn Bock and the Zone of Belemnitella plena, 

 from Cambridge to the Chiltern Hills." By W. Hill, Esq., F.G.S., 

 and A. J. Jukes-Browne, Esq., F.G.S. 



The " Melbourn Bock," which was first defined by one of the 

 authors in 1880, is a band of rocky chalk which forms the base of 

 the Middle Chalk in Cambridgeshire, and occurs about 80 feet above 

 the " Totternhoe Stone." In the present paper it was shown, as the 

 result of the mapping operations of the Geological Survey, to form 



