On two Boulders of Granite from the Middle Chalk of Betchworth, Surrey

Abstract

Boulders of various Palæozoic rocks, other than mere pebbles, in the Upper Cretaceous and in some other strata have at different times been described, but they are acknowledged to be of comparatively rare occurrence in rocks of Mesozoic age. It may be of interest to summarize briefly the chief finds of this kind which have been made up to the present in this country. In 1827 Mantell observed that ‘In this country the Chalk very rarely contains traces of older deposits: the only instances of extraneous rocks that have come under my observation are pebbles of quartz and some fragments of green schist.’ In 1850 Dixon wrote:—‘Small pebbles and large rolled fragments of sandstone and quartz-rock are occasionally discovered in the centre of the Upper Chalk. Mr. Coombe found one specimen, weighing near 14 lbs., at Houghton, Sussex, and I have seen others from the same pit of 2 or 3 lbs. weight. Several also have been sent me by Mr. Catt from the pits near Lewes.’ In 1857 the well-known Purley boulder was found, of which this Society is fortunate enough to possess the principal remains. R.A.C. Godwin-Austen in vol. xiv. of the Quarterly Journal, p. 253, says ‘the boulder ..... was found in a chalk-pit by the side of the old London and Brighton road, near Purley..... The portion of the Chalk-formation in which the pit it worked is the lower part of that containing flints.’ After the boulder was removed there were found associated with it a