196 MR. J. A. EROWN OK THE THAMES-VALLEY 



peculiar way as to suggest that such erosion was effected by crenic 

 and other acids associated with humus. The bleached surface, more 

 particularly of the larger stones, is often on the upper side only, 

 while the under surface has the same colour as the gravel, that is, 

 ochreous or brown, as the case may be. Some of the stones, however, 

 do not appear to take the staining easily and remain black, as is the 

 case with many of the flint implements. 



The presence of this coating of black matter on the stones and 

 grains of sand, together with the humus, which hides their bleached 

 surfaces, seemed to me to form a reasonable basis for the hypothesis 

 that these seams represent old land-surfaces ; and this hypothetical 

 suggestion became to me almost a matter of certainty when un- 

 abraded flint implements &c. were found at levels corresponding 

 with them. 



The bleached stones, porcellanized only on the outer side, indicated 

 that they had been exposed to the sun's light and to the atmosphere 

 for a long period ; and the whitened fragments which are often found 

 scattered through the gravel without being associated with any par- 

 ticular line of stratification show that these old land-surfaces had 

 been again and again broken up and disturbed, and with them these 

 flint implements, which have become more or less abraded owing to 

 their having been carried about by currents from one spot to another. 



Three or four more or less distinct lines of former land-surface 

 have been traced by me in various sections between Creffield Road, 

 Acton, and Longfield Avenue on the rise of Castlebar Hill, Ealing. 

 One occurs at a level of from 4 to 6 feet below the surface, a second at 

 from 7 to 8 feet, and a third (a black seam) at from 10 to 14 feet. 



Although some of the unabraded implements and flakes in my 

 collection had been found at levels corresponding with these floors, 

 yet the majority of those hitherto discovered were more or less 

 abraded and rolled, so that it was not until the ground was exca- 

 vated in the Creffield Road, Acton, at about 100 feet above 0. D., that 

 my views were entirely confirmed. 



The gravel-pits in the Creffield Road, Acton, are situated near 

 where that road is intersected by Mason's Green Lane, about 200 

 yards south of the bridge over the Great Western Railway ; the 

 surface of the ground is nearly horizontal, but with a very slight 

 incline towards the Thames, which now flows in a curve in this 

 direction about two miles away as the crow flies. 



In two small pits, one about 18 feet square, and the second 30 x 12, 

 situated within 6 or 7 yards of each other, the workmen discovered, 

 close beneath the brick-earth deposits, and about 6 feet from the sur- 

 face, about 400 implements, flakes and fragments, while at the second 

 level of 8 feet, five or six specimens were met with, and at from 10 

 to 11 feet three specimens rewarded me for the continued care I had 

 given to this locality. It soon became evident that there had been a 

 manufactory of Palaeolithic implements on this uppermost floor, since 

 they were often found together in nests, and they are all as sharp 

 and unabraded as on the day they were made. 



The underlying gravel, which at the period of its deposit formed 

 the land-surface, and is composed of the usual subangular stones, slopes 



