Prof. S. H. Reynolds — Serpentine near Wells, Somerset. 225 



finding a piece in 1914. No pieces have been detected in any of the 

 neighbouring wallS; and the neighbourhood has been so carefully 

 examined that if the rock occurred in situ it could scarcely fail to 

 have been found.' 



The country rock forming the fields where the picritic serpentine 

 occurred is the Dolomitic Conglomerate, and another possibility 

 which suggested itself was that we might be dealing with a 

 pre-Triassic intrusion, and that the pieces found were pebbles in the 

 Dolomitic Conglomerate.- To test this the Dolomitic Conglomerate 

 was exposed by means of trial-holes at a number of points in the 

 principal field, but no fragments of picritic serpentine were ever 

 found. 



The only remaining alternative to account for the presence of 

 the rock is that it was brought from a distance and jDresumably 

 from Menheniot. The suggestion that it was brought by human 

 agency may, I think, be dismissed. Another explanation, and 

 jDcrhaps the most probable, was suggested in conversation by 

 Professor Bonney, viz. that the pieces were derived from an ice- 

 borne boulder. 



The acceptance of this theory implies great submergence of the 

 South of England, as the pieces occur at a height of 375-85 feet 

 above Ordnance datum. It may, however, be recalled that Dr. J. V. 

 Elsden ■'' in 1887 described a granite boulder from Kithurst, in 

 Sussex, which was found at the 600 ft. contour-line at the summit 

 of the Chalk escarpment. The transport of material probably from 

 Cornwall, which this theory involves, is also perhaps a difficulty, 

 as the great majority of the foreign boulders on the south coast of 

 England, which apj^ear to owe their presence to floating ice, seem to 

 have come from the north-east.'' On the other hand the erratic 

 blocks collected by Mr. Clement Reid from the Pleistocene deposits 

 of Selsey, included rocks which reminded Professor Bonney ^ of types 

 met with in Brittany, and one specimen was probably of Cornish 

 origin. It is not, however, necessary to assume that such a sub- 

 mergence took place in Pleistocene times ; the height at which the 

 j)ieces of j^icritic serpentine were found is very much that of the 

 platform rising to the 430 ft. level, which has been recognized along 

 much of the southern part of the British Isles, from Ireland, through 



' Mr. Balch, however, writes (June 14, 1914) : " I am not at all convinced 

 that the ice transport theory can hold. ... 1 am strongly inclined to suspect 

 an intrusion, small and so far not detected." 



* This is the explanation suggested in a jiaper by the author read before the 

 British Association at York in 1906 (Trans, of Section 0, p. 581). There is 

 also a brief account of the rock in the author's Geological Excursion Handbook 

 for the Bristol District, 1912, p. 119. Mr. Balch shows the area in which the 

 picritic serpentine was found in his Wookfi/ Hole, pi. vi. 



^ Quart. Journ. Geol. 8oc., vol. xliii, 1887, pp. 649-51. 



* R. A. C. Godwin-Austen, Quart. Journ. Geol. Soc, vol. vi, 18.50, p. 88. 

 J. Prestwich, ibid., vol. xlviii, 1892, pp. 295-8. G. Barrow, The Geology of the 

 Isles of Scilly (Mem. Geol. Surv., Sheets 357 and 360), p. 24. 



° Quart. .Journ. Geol. Soc, vol. xlviii, 1892, p. 351. 



VOL. LVII. — NO. V. 15 



