^{page 79 note 1} The Relative Ages of the Stone Implements of the Lower Thames Valley, by Hinton, M. A. C. and Kennard, A. S., Proc. Geol. Assoc., Vol. XIX., pp. 76–100Google Scholar.

^{page 79 note 2} Stratification of Swanscombe, by Smith, Reginald A. and Dewey, Henry. Archælogia, Vol. LXIV, pp. 177–204Google Scholar.

^{page 79 note 3} I have obtained implements in situ in this position on several occasions, together with many thinning flakes. The existence of unworn implements and many flakes (although I have not succeeded in fitting any together) show that implements were made on the spot. The flakes differ in many respects from those forming the subject of this paper.

^{page 79 note 4} Loc. cit. p. 180 et seq.

^{page 81 note 1} I have two specimens very similar to this.—R.H.C.

^{page 81 note 2} Exposé de titres et bibliographie (1929), p. 21Google Scholar. The name “Clactonian” was suggested bv Mr. Warren himself in 1926 for this industry at Clacton, owing to the original Mesvinian being capable of sub-division into two stages, and the Abbé Breuil confining the Mesvinian to the later stage. Presidential Address to the S.E. Union of Scientifiic Societies, 1926, pp. 38–51Google Scholar.

^{page 81 note 3} The Mesvinian Industry of Clacton-on-Sea, Essex, by Warren, S. Hazzeldine. Proc. Prehistoric Soc., East Anglia, Vol. III., pt. 4, pp. 597–602 (1922)CrossRefGoogle Scholar.

^{page 83 note 1} Loc. cit. p. 21.

^{page 83 note 2} It is to be noted that the Abbé Breuii is here speaking of “flakes.” I must add that when I shewed him the collection illustrated in this paper he expressed the opinion that they were only flakes and cores.

^{page 83 note 3} The large flints do not occur in the middle gravel, and I have obtained in situ examples of each type of tool, variety of flint, and patiuation found in the heaps.

^{page 83 note 4} On one occasion I saw 4ft. 6ins. of tusk exposed in the upper part of the lower gravel; it was 6¼ins. in diameter at the broken end, and had a curve of about 6ins. in 4ft. 6ins. It was too decayed to attempt to get total length, and the face was dangerous owing to frost. I only remember seeing one straight tusk in lower part of lower gravel.

^{page 84 note 1} The fact that the workmen do not recognise the cores and flakes is an advantage to the student.

^{page 84 note 2} The Experimental Investigation of Flint Fracture and its Application to Problems of Human Implements. Journ. Royal Anthropological Inst., Vol. XLIX., pp. 412–450 (1914)Google Scholar.

^{page 86 note 1} Loc. cit. p. 602.

^{page 86 note 2} The Pleistocene Deposits and their contained Palæolithic Flint Implements at Foxhall Road, Ipswich, by Boswell, P. J. H. and Moir, J. Reid. Journal of the Royal Anthrop. Inst., Vol. LIII., pp. 229–262 (1923)Google Scholar.

^{page 86 note 3} As a general rule one may say that the higher the flaking angle the less protuberant the bulb, so that in flakes having an angle of 140° there is hardly any swelling at all, but in flakes of 115° or less the bulb is protuberant. Exceptions to the rule are not uncommon.

^{page 87 note 1} By prominent bulb of percussion I do not mean large and protuberant bulb (although some occur) but that the upper part of the cone is free and projects beyond the general line of the bulb face, so that from half to three-quarters of a circle of flint is seen at the apex of the cone when looking at striking platform on plan. See fig. “C.” In one flake this feature is so accentuated that the upper few mm. of cone is entirely free and the flat apex of cone (which is in the plane of the striking platform) is separated from the striking platform by a slight notch.

^{page 87 note 2} The human hand being so adaptable this point may not be of much value.

^{page 87 note 3} Archæologia, Vol. LXIV., p. 183Google Scholar.

^{page 87 note 4} The Abbé Breuil has met this problem in his latest pronouncement (published after the reading of this paper) by stating the early part of the Clactonian culture preceded the maximum Mindel glaciation, and that the Clactonian lasted on until the opening of the succeeding interglacial time. This conclusion he arrived at from a study in the neighbourhood of Cambridge and Ipswich. La Préhistoire—Lecon d'ouverture de la chaire de préhistoire au Collège de France. La Revue des Cours et Confèrences (30, XII. 1929). Thus M. Breuil accounts for both the contemporary and the derived series and, by inference, explains the difference between the two series of flakes by a difference in age. The earlier and derived flakes (with an average flaking angle of 109°) being glacial (Mindel), and the contemporary ones (with an average flaking angle of 122°) being interglacial. This is the conclusion I have drawn from the study of Barnfield Pit. See Summary and Conclusions below.

^{page 90 note 1} The High Terrace of the Thames, by Smith, Reginald A. and Dewey, Henry. Archælogia, Vol. LXV., pp. 187–212 (1914)Google Scholar.

^{page 90 note 2} In looking through the material obtained during the official excavations at Dierden's Pit and now preserved in the British Museum, I found one flake having an angle of approximately 150°; it is the highest angle I have ever seen and there were many other flakes having angles as high as those I have obtained in Barnfield Pit.

^{page 90 note 3} At Dartford Heath, where these Bunter quartzites are common, they are associated with many igneous rocks, Carboniferous cherts and other material derived from areas beyond the present Thames basin, and have been regarded as being derived from glacial deposits. Proc. Geol. Assoc. Vol. XX., pp. 122–128 (1907)Google Scholar. But see also re Triassic debris, White, H. J. Osborne, On the Origin of the High-Level Gravel with Triassic Debris, adjoining the Valley of the Upper Thames. Proc. Geol. Assoc. Vol. XV., pp. 157–174 (1897)Google Scholar Igneous rocks also occur rarely in the gravels of the Swanscombe area.

^{page 90 note 4} The difference in level between Clacton and Swanscombe is difficult to explain. The distance between Swanscombe and Clacton being about 40 miles allows a fall of 27 inches per mile, assuming that both deposits are due to the same river. The industry has yet to be found at intermediate heights between these two places.

^{page 90 note 5} Many of these flakes struck me as being similar to some I had seen in the glacial beds of East Anglia and I sent some of the derived series to Mr. J. Reid Moir. He replied as follows:—“……; very similar flakes exhibiting the same type of glare, striation and workmanship, occur in the glacial gravel underlying the upper Chalky Boulder Clay of this district [Ipswich]. This gravel rests at about 120 ft. O.D. and I am satisfied that your specimens compare in all essential points with tho e from the deposits mentioned. I have also found in this gravel a core very similar to that which you send. Further, I am now getting a large number of comparable flakes from the gravel overlying the Contorted Drift of Cromer, which gravel I correlate with that underlying the Upper Chalky Boulder Clay here …… Your specimens shew the large flatfish striking platforms, and the kind of edge flaking present upon the flints from the glacial gravels I mention……” Since receiving Mr. Reid Moir's opinion I have re-visited some of the glacial gravels of East Anglia (Cromer, Warren Hill and Bramford) and collected flakes, and also seen the splendid collection in Ipswich Museum. There is a distinct similarity and the high flaking angle is noticeable, but I do not wish to push the evidence too far.

^{page 92 note 1} Later glacial stages represented by the Cold Mousterian, Coombe Rock, Trail, etc., and earlier glacial stages are outside the scope of this paper.

^{page 93 note 1} Mr. Hazzledine Warren has urged me to use the measurement of the external flaking angle X Y Z (fig. on p. 85) or, what comes to the same thing, the core angle V X Z, in preference to the inner flaking angle Y X Z, when describing the characteristics of the flakes mentioned in the foregoing paper. Mr. Warren urges this on the grounds that the external flaking angle is easier to measure and that by so doing one visualises the original shape of the core, or implement, before the flake was detached, and the picture of the process. This may be so, but when using my method one at once sees the supplemental angle, which is the one to which Mr. Warren refers. Furthermore, as so many of the flakes in the Clacton culture at Barnfield Pit have cortex on the external side the external angle is difficult to measure (the industry being crude and the implements so often the result of the removal of the cortical flakes); it is only by measuring the internal flaking angle that it is possible to describe them, and to call attention to the point for which they are peculiar. It is true that my use of the words “high” and “low” angles without the explanation in text and diagram might be confusing, and may be contrary to current practice, but it is for that reason that the particular use is explained. As mentioned above, the angle X Y Z has frequently the side Y Z of cortex, and the measurement of this angle would convey nothing but an idea of the shape of the cortex of the nodule. Moreover, the angle X Y Z has little do with the result of the blow which fell at X. It is on the result of the blow at X that we are concerned with in the flakes under discussion.