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EXCURSION TO MAIDE~HEAD AND BRAY CUT. SATURDAY, MAY IITH, 1918. REPORT BY C. N. BnoMEHEAD, B.A., F.G.S., F.R.G.S., Director at the Excursion. A P.-\RTY of nearly twenty assembled at Station .at 1-48, and walked towards Kimber's House. By the turning to the director pointed out the general features of the landscape-to the south-east lay the high ground of Windsor Forest with St. Leonard's Hill, Where the London Clay is capped by a thin outlier of Bagshot Sand. The Thames was not visible, but the plateau crossed on the way from the station, on the edge of which the party were standing, was formed by the gravels of the Boyn Hill (100 foot) Terrace of the Thames, about 70 feet above the present water-level. The Taplow (50 foot) Terrace could be seen on the far side of the valley of the Bray Brook, and Mr. Treacher mentioned that a gravel pit recently re-opened yielded rolled implements derived from the higher terrace. Although near the railway the Boyn Hill gravel rests directly on chalk, near Kimber's House a considerable thickness of Reading Beds intervenes. Springs thrown out from the gravel by the clayey beds were visible in the roadway. The walk con­ tinued across fields, in places very marshy, to Stud Green. Here the old brick works Were noticed, but the pit is now full of water. The section formerlv visible was:- Sandy Brick Clay,S ft. Bands of Sandstone, I ft. Brick Clay, 9 ft. Mottled Clav. This is of interest, as the sandstone, only I ft. thick, appears to be the equivalent of the many bands of sandstone, several exceeding 2 ft. in individual thickness. seen in Bray Cut, showing dearly how local is the latter development. Several of the picturesque half-timbered crofters' cottages, relics of the time when the district was included in the area of Windsor Forest, attracted attention. Paley Street Bridge was the next point of interest. Here the stream flowing through the Cut enters upon a natural course. Mr. Treacher remarked that the Cut Was engineered by his great-grandfather, 1\1r. John Treacher, of Sonning, the County Surveyor, the latter's son, Mr. George Treacher, being the contractor. Mr. Treacher kindly placed at our disposal a number of documents concerned with the work, from which many of the following particulars are taken. C. M. BROMEHEAD,

The Forest Stream, which now flows through the Cut, rises. near Swinley and Englemere Pond. During its course to Brick Bridge (on the road between .Redstone Farm and Beenharu's Heath) it collects the drainage of 25 square miles, including Jealott's Hill, \:rarfield, Winkfield, Easthampstead, Caesar's Camp, and Bracknell. From Brick Bridge the original course Was through .Ruscombe and Hurst to join the Loddon at Twy­ ford, and so into the Thames at Wargrave. The fall in this lower course Was'very small; the stream, draining a clay country, filled up very rapidly after rain and consequently overflowed its banks. An area of 3,000 acres was always marshy and frequently flooded, much like the small area near Thrift Wood, painfully crossed by the party. The remedy suggested Was the making of an artificial cut from Brick Bridge to the Shaffield Moor Brook near Paley Street, a distance of about one mile. The water would then flow through Bray Wick to join the Thames at Queen's Eyot. The distance from Brick Bridge by this route is less than six miles, by the natural route 29 miles, being eight miles to the Thames and 2t from Wargrave through Henlev and Marlow to the new mouth. The fall is 50 feet. The work Was estimated to cost £5,500, those concerned agreeing to raise the money bya voluntary rate. Unfortunately, some of it has not heen raised yet! but the Work was begun in 1817 and finished in 1822, to the great benefit of the land drained. A further benefit is to be found in the lessening of the floods in the Loddon and the Thames near Wargrave; as the Loddon is still frequently flooded, this factor is by no means to be despised. It will be observed that the change in the natural drainage by which the stream is given a quicker immediate fall is a typical case of river-capture-produced by artificial means; of the fall of 50 feet between Brick Bridge and Oakley, the greater part, roughly 40 feet, is in the artificial cut, that is to say, in a distance of one mile. Naturally a considerable body of Water with such a fall is capable of doing a good deal of work on its course, which is undoubtedly being deepened at the present day. This action, coinciding with the outcrop of the hard sandstone beds described below, has led to" the formation of the picturesque " glen" into which the Cut has been converted; the numerous ledges of rock, with cascades over them and deep pools below', are unlike anything else in the London Basin, and more snggestive of the scenery in the Palaeozoic regions of Wales or Scotland. Plate II. in the Memoir on the district is a photograph of one of the cascades. After a welcome rest on the grassy bank the more energetic members of the party examined the rocks exposed; a generalised section is as follows :- Brown London CIa,', EXCURSION TO MAIDENHEAD AND BRAY CUT. 139

Pebble Bed with shells, ~ ft. Sand and Clay with bands of Sandstone, 12 ft. Mottled (Reading) Clay, 20ft. The hard bands consist of fine-grained calcareous Sandstones with a certain amount of white mica. Occasionally this rock is full of Ditru-pa plana. No specimens were found in situ during the excursion, but a few were picked up from the surface of the ploughed field, together with oysters and other shells from the pebble-bed. The Clearest exposure was on the far side of a deep pool into which the stream fell over a three-foot ledge of Sand­ stone, and could only be examined from the bank. A list of fossils collected here by Warburton is given by Prof. Prestwich.* The party left the Cut at How Lane Bridge and returned by the road to Paley Street village; the old lane known by that name Was taken, and at Paddock Wood the strong feature formed by the Basement Bed of the London Clay, with sandstone bands, was noticed and the main features of the landscape pointed out. The walk continued partly across fields to Cox Green. In ascending Lock Lane to Shoppenhangars, the chalk was noticed in an old pit beside the road; it belongs to the zone of M. cor­ IJnguinum: above this Were traces of the Reading Clays followed by the Boyn Hill River Gravels forming the plateau. At the Station the party broke up, but several members had tea together in Maidenhead. Mr. A. H. Williams acted as Excursion Secretary.

REFERENCES. Maps, rin., Geological Survey, Old Series, Sheet 7. Ordnance Survey, Small Series, Sheet 269 (Windsor). Ordnance Survey, Large Series, Sheet II5. 1915. DEWEY, R., and C. N. BROMEHEAD.-"Geology of Windsor and Chertsey;" Mem. Geol, Suru .

• Qnnrt, JO/l1'1/. Gcol. xoc., vol 18; . 6].