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KRONOS Vol V, No. 1
The Kintraw Stone Platform
Professor Thom's innovative hypothesis concerning megalithic astronomical observatories has, if correct, catastrophic import on a range of disciplines. His works have consequently provoked considered opposition from various quarters.(1) A fundamental criticism which is often levelled at his work concerns the absence of independent evidence, anthropological as well as archaeological, which would necessarily underpin his theories. This dilemma seemed to have been resolved in 1969 when Thom stated that a small ledge had been cut into the steep hillside at Kintraw for use as an observation platform.(2) An archaeologist, Dr. Euan MacKie, reasoned that the ledge provided a crucial test for the veracity of Thom's ideas; for if the ledge was artificial, or if traces of prehistoric activity were to be found there, this would constitute archaeological proof of the astronomical theories.(3)
Dr. MacKie's subsequent excavations on the ledge were, however, disappointing and, indeed, embarrassing. Not only was the ledge found to be undoubtedly natural,(4) there was an utter lack of the "normal archaeological signs of human activity – no potsherds or artefacts of any kind were found during the excavations, nor any fragments of charcoal such as might have come from fires. Neither were there any signs of postholes, kerb stones or any structural remains".(5) A compact layer of stones was, however, discovered behind a couple of boulders that could have been the hypothetical backsight for the supposed observatory. A soil scientist, Mr. J. S. Bibby, performed a petrofabric analysis on two sections of this layer and compared the resultant contours visually with three others two natural formations from Broadlaw, Peebleshire, and one manmade formation from Sheephill Fort, Milton, Dunbartonshire. His conclusion was that "the available evidence supports the hypothesis that the Kintraw platform was man-made".(6) It is on the strength of this statement that several commentators have pronounced the positive vindication of Thom's archaeo-astronomical thesis.(7)
Mr. Bibby reasoned that, since the contours obtained from Kintraw are broadly similar to that from Milton, but dissimilar to those from Broadlaw, the implication is that the Kintraw platform was artificial. It is exceptional that the apparent corroboration of such a potentially important hypothesis, as Thom's undoubtedly is, should depend on the conclusion drawn from such a fragile argument. Indeed a careful scrutiny of the available evidence pertaining to the limitations of, and errors inherent in, the petrofabric technique, suggests that Mr. Bibby's statement is incorrect. This conclusion is validated when note is taken of the shortcomings in Mr. Bibby's method of obtaining petrofabric contours. A review of such evidence is given below.
Petrofabric analysis is a well established technique used for qualitative descriptions of various formations. In an authoritative overview,(8) W. C. Krumbein analysed the limitations of petrofabric analyses, and offers the following observations:
Krumbein also criticises conclusions based on the evidence of a limited number of petrofabric samples.
Compare these statements with the decidedly sparse information presented by Mr. Bibby: Five contours; no accompanying statistical data; Broadlaw and Kintraw, although geographically adjacent, are geologically dissimilar; the sites at Broadlaw were above 450m in altitude, that at Kintraw only 45m.
The limitations inherent in petrofabric analyses, the paucity of information offered, and the geological diversity between Broadlaw and Kintraw mitigate severely against Mr. Bibby's conclusion.
Even allowing for the above, and accepting that petrofabric analyses may have limited use as a descriptive geological tool, doubt must be expressed as to the accuracy and dependability of the techniques employed by Mr. Bibby in acquiring his contours. For this purpose a review of the standard petrofabric technique is given.
Petrofabric analysis involves the translation of three dimensional information concerning the azimuthal direction and angle of dip of the stones from the strata being investigated onto a two dimensional mesh. The analysis requires precise definitions of the axes and planes of the stones so that the data is objective and reproducible. Rigorous experimental techniques have therefore evolved.
At the site being investigated, measurements are made of the direction of the ground surface (direction of slope or aspect) with respect to north, and also of the inclination of the ground to the horizontal (angle of slope). Excavation of the site takes place and one or more layers of stones may have petrofabric analyses performed on them. From each stratum being investigated, a sample of 100 stones is selected for measurement. Vertical and horizontal lines are drawn on these stones when in situ relative to the fixed axis of true north. The stones are then systematically collected and removed to the laboratory where the two most commonly moved axes – the long axis a and the short axis c – are accurately determined. The absolute azimuth and angle of dip of both these axes are then found and these are plotted onto separate equareal (polar equal area) nets – see Fig. 1. The azimuthal direction is measured clockwise around the circumference, the angle of dip decreases outwards radially from center to the circumference. Stones having vertical axes will be at the center of the net, those with horizontal axes will occupy diametrically opposed points on the circumference. The percentage concentration of points per unit surface area is found and contouring is performed round areas of like density. In any accurate study of petrofabric contours, diagrams of both the a and c axes should be presented.
In their study of natural soliflucted layers at Broadlaw,(12) Bibby and his co-worker Ragg investigated five sites at altitudes above 450m and petrofabric analyses were performed on different stratum levels at each site. A 10-20cm zone across the face of each layer was selected and the orientation of 100 stones recorded with the aid of a prismatic compass and clinometer. The long axes of the stones were determined by inspection as a large proportion were tabular in shape. At Kintraw two areas were selected on the exposed pavement, each measuring 50cmX50cm, and again the a axis of each stone was found by inspection, the inclination being obtained from an Abney level. Only stones over 3cm in length were selected as smaller stones proved difficult to handle and measure. The stones were predominantly tabular or wedge shaped. No information is available concerning the contour obtained from the man-made pavement at Milton. However one presumes that a similar technique was used there.
A major flaw appears in Mr. Bibby's technique for, as shown, the long axis a was determined by visual inspection and not by precise laboratory techniques using a goniemeter. Again the important c axis was not determined. When consideration is taken of the errors inherent in the method even when using the most rigorous experimental techniques, greater errors are to be expected when using visual inspection only. In an attempt to quantify the errors involved, Harrison,(13) using small stones (3-40mm), found that the least error involved was as much as 6° on the average for pole plots and 7-8° for plots of axis. These are the minimum errors involved in careful laboratory work. The contours presented by Bibby must therefore be even more inaccurate.
The final flaw in Bibby's analysis is exposed when one considers in detail how he came to the conclusion that the evidence pointed to the Kintraw platform being artificial. This conclusion depended on the judicious selection of contours obtained from Broadlaw while regarding as axiomatic the following arbitrary assumptions:
(a) That only man-made formations show wide variations in the direction of dip of the a axis and relatively low angles of inclination.
(b) That natural formations are utterly influenced by the direction of the slope as well as the dip of the slope in which they are found. Conversely man made formations show little influence of the slope or the direction of the ground surface.
The two contours obtained from the Kintraw site (Figs. 2 and 3) were compared to a hitherto unpublished scree formation from Broadlaw (Fig. 4), a contour of a man-made platform from Sheephill Fort, Milton, Dunbartonshire (Fig. 5), and a contour of a soliflucted layer also from Broadlaw (Fig. 6). Mr. Bibby's conclusion is based on the apparent similarity of Figs. 2 and 3 to Fig. 5 – both show wide variations in the angle of dip and low angles of inclination when compared to the Broadlaw contours. They also appear to be influenced to a lesser degree by the characteristics of the ground surface in which they are found than do the Broadlaw contours.
At first appearance, one tends to agree with the above reasoning. However, a closer scrutiny of the 1966 paper by Ragg and Bibby on the soliflucted layers at Broadlaw discloses detailed evidence that contradicts Mr. Bibby's reasoning. Ragg and Bibby presented twelve contours obtained from the analyses of a number of strata at each of five sites (labelled I to V). These twelve contours are equally distributed into those showing strong orientation, weak orientation, and no orientation relative to the direction and angle of the slope (or ground surface) in which they were found. Interestingly, Fig. 6, the contour selected for comparison purposes, displays the most strongly orientated contour of the twelve with regard to the parameters of direction and angle of the slope. This contour was taken from site II at a depth of 95-105cm beneath ground surface. If one observes the contour obtained from the stratum level immediately beneath it, described as similar except that its stones are larger (Fig. 7), one sees markedly less orientation. Another two contours from Broadlaw are also given. Fig. 8 shows a layer at site IV (depth 140-160cm) and Fig. 9 a layer at site V (depth 280-300cm) which show a better resemblance to the Kintraw contours than to Fig. 6. Clearly, Mr. Bibby's statement that natural formations always show strong orientation relative to the slope in which they are situated is incorrect.
Mr. Bibby's hypothesis that wide variations in the angle of dip and relatively low angles of inclination of the a axes are synonymous with man-made formations is based on conjecture, and conjecture only. Figs. 8 and 9 prove this (as they disprove Mr. Bibby's conjecture). Fig. 10, meanwhile, shows a contour taken from a layer of outwash pebbles occurring in a late Wisconsin terrace near Cary, Illinois. According to Mr. Bibby's criterion, the petrofabric contour of this terrace should prove this outwash to be a man-made formation. This sample, taken from a single gravel bed that sloped 12° compares favorably with the 10° slope of the Kintraw platform and the 5° slope of the Milton man-made pavement. This suggests that, at sites with angles of slope (10° or less), these low angles of slope influence the shape of petrofabric contours much more significantly than the method of formation of the strata from which these contours are obtained; and this conclusion seems more valid than the one arrived at by Mr. Bibby. Both of these conclusions, however, are necessarily invalid for they are based on an improper and indiscriminate use of petrofabric analysis.
If we refer to the beginning of this article we see that single samples are of limited value in studying different environmental conditions. To this we may add another comment by Krumbein.
In the light of this statement, we see that any conclusions based on the comparison of a limited number of contours have no weight. For example, no systematic work had been performed on the petrofabric contouring of samples taken from man-made formations. In fact the only available petrofabric contour of an artificial formation was that performed at Milton. From this single contour Mr. Bibby decided that the site characteristics had little influence on man-made formations, and that such formations should have wide variations in the angle of dip and low inclinations of the a axis. But no conclusion can be drawn from a single contour – chance occurrences as described above could make this single contour resemble any other contour, natural or artificial. As demonstrated above, if we were to judge by Mr. Bibby's criterion, the Wisconsin outwash pebble contour shown in Fig. 10 would be a perfect example of an artificial formation.
In conclusion, we will have to admit that no valid evidence has been presented in support of Professor Thom's hypothesis concerning the function of the Kintraw ledge. It is not, as he declared in 1969, artificial. No traces of archaeological litter concomitant with the supposed importance of the ledge were found. And finally, the claim that the excavated stone platform was man-made is clearly wrong. It therefore appears that the first organized activity on the Kintraw ledge took place in the last decade; indeed, the very absence of any prehistoric activity on the ledge is a damning indictment of the astronomical significance of the ledge in particular and the Kintraw megalithic site in general.
FIGURE CAPTIONSFig. 1. Polar equal area net
Fig. 2. Kintraw No. 1: Direction of ground surface 240°; angle of slope 10°.
Fig. 3. Kintraw No. 2: Direction of ground surface 240°; angle of slope 10°.
Fig. 4. Broadlaw scree: Direction of ground surface 175°; angle of slope 37°.
Fig. 5. Sheep Hill Fort: Direction of ground surface 163°; angle of slope 5°.
Fig. 6. Broadlaw soliflucted stone horizon (Site II): Direction of ground surface 305°; angle of slope 16°.
Fig. 7. Broadlaw soliflucted stone horizon (Site II): Direction of ground surface 305°; angle of slope 16°.
Fig. 8 Broadlaw soliflucted stone horizon (Site IV): Direction of ground surface not kown; angle of slope 9°.
Fig. 9. Broadlaw soliflucted stone horizon (Site V): Direction of ground surface 270°; angle of slope 17°.
Fig. 10. Cary outwash pebbles: Direction of ground surface 180°; angle of slope 12°.
Figures 1 to 6 adapted from J. S. Bibby's "Petrofabric Analysis," Philosophical Transactions
of the Royal Society of London, 276 (1974), p. 192.
NOTE: As the Figures 1-10 came from different sources, every attempt has been made to adapt them as accurately as possible from the originals.
REFERENCES1. D. Cardona, "The Stones of Ballochroy," KRONOS,Vol. IV, No. 3, pp. 23-37; Idem, "The Cairns of Kintraw," Ibid., pp. 38-55; T. McCreery, "Megalithic Lunar Observatories – A Critique," KRONOS,Vol. V, No. 1, pp. 47-63 and Vol. V, No. 2, pp. 6-26; A. Fleming, Nature (June 19, 1975), p. 575.
2. A. Thom, Vistas in Astronomy, 11 (1969), pp. 7-9 where the author states that the "little platform [was] cut into the very steep hill" and describes it as "like a short length of narrow road". He also notes: "There is little wonder that the erectors did not mind cutting the auxiliary platform and then perhaps raising the viewpoint at the main site once the exact spot had been found by observations from the platform."
3. E. W. MacKie, "Archaeological Tests on Supposed Prehistoric Astronomical Sites in Scotland," Philosophical Transactions of the Royal Society of London, 276 (1974), p. 180.
4. Ibid., p. 181.
5. Ibid., p. 183.
6. J. S. Bibby, "Petrofabric Analysis," in Ibid., p. 194.
7. E. W. MacKie, Science and Society in Prehistoric Britain, London (1977), p. 92; J. Edwin Wood, Sun, Moon and Standing Stones (Oxford, 1978), pp. 87-90.
8. W. C. Krumbein, Journal of Geology, 47 (1939), pp. 673-706.
9. Ibid., p. 674.
10. Ibid., p. 682.
11. Ibid., p. 705.
12. Ragg and Bibby, Geografiska Annaler, 48 A (1966), pp. 12-23.
13. Harrison, Journal of Geology, 65 (1957), pp. 98-105.
14. W. C. Krumbein, op. cit., p. 698.