I had not intended to reply to Professor Holmes's recent paper in the Geological Magazine, but the apparent confusion of mind which exists about the question of contrasted differentiation has led me to do so.

Between Kennedy's Pass, 4 miles south of Girvan, and Currarie Port, 3½ miles south of Ballantrae, the coast is occupied by a varied assemblage of igneous rocks that have a north-easterly strike and extend inland for several miles (Text-fig. 1). The most important members of this assemblage are a series of spilite lavas and two large outcrops of serpentine. In the present paper it is not intended to give a general description of these rocks, but to concentrate upon the age-relationship of the serpentine to the lavas and associated sediments, in which Lapworth and later workers discovered Arenig fossils.

Among other parallels to the structures which he regarded as “crush-conglomerates” in the Manx slates, G. W. Lamplugh (1895, 586–7) mentions beds with isolated fragments in the Bray Series, at Howth, Co. Dublin. The age of this Series of slates and quartzites is rather conjectural. Fossil evidence, founded on such forms as Oldhamia, though supplemented by W. J. Kyan and T. Hallissy, who suggest Middle Cambrian (1912, 249), is inconclusive. More recently, E. Greenly proposes a pre-Cambrian age (1919, 896). The alternating (or greywacke) type of sedimentation seen in the beds recurs many times during Dalradian, Cambrian, Ordovician, and Silurian. Two schools in the interpretation of the Series have to be considered. The older school, with J. Kelly (1853, 240, 253–262) and G. H. Kinahan (1878, 12, 14) as its adherents, ascribed the fragmentation in the shaly beds to volcanic agencies, and, since they failed to distinguish cleavage from bedding, regarded many of the quartzites as intrusive. The younger school, including A. McHenry and W. W. Watts (1898, 17) and Lamplugh (1903, 6), described the breccias as produced by friction during regional earth-movements. The latter, as W. J. Sollas puts it (1893, 98), possibly extended from post-Ordovician to post-Carboniferous. While the effect of later crushing and faulting must not be overlooked, it seems necessary i n the light of recent work by E. B. Bailey (1930, 86–90), Bailey and J. Weir (1932, 429–458), and S. M. K. Henderson (1935, 487–509), t o invoke probable seismicity and contemporaneous slumping to explain the alternating beds and associated shaly breccia. A new suggestion will be advanced regarding the quartzites.

Both geologists and archaeologists will be under a debt of BOTH gratitude to Messrs. King and Oakley for their recent paper on the Pleistocene sequence of the lower part of the Thames Valley (I). Not only have they conveniently summarized the results obtained by other field-workers, but they have contributed two postulates of great importance. These are: (a) the probability of a major period of erosion between the deposition of the Lower Loam and the Middle Gravel of the Boyn Hill Terrace succession; and (6) the recognition of a period of erosion between the formation of the Lower Flood Plain Gravel and the Post-Pleistocene alluvial beds.