FOR the past two winters it has been the author’s good fortune to undertake the geological work for Miss Caton-Thompson’s investigations into the prehistory of Kharga Oasis. This necessarily involved a close consideration of the water supply in Pleistocene times, the results of which disclosed some interesting new facts and raised climatic questions of more than local interest.

THE late Dr. Vaughan, in 1905, established the age of the sand-stone lying above the Whitehead Limestone of the Forest of Dean as of upper Seminula age, and not, as had been supposed, as the equivalent of the Millstone Grit. Later, in 1912, Dr. T. F. Sibly described the sandstone as “ composed very largely of pure quartz sandstones, often coarse-grained and friable. Conspicuous bands of quartz conglomerate occur: some clays and shales are intercalated, with the sandstones: and some haematite deposits are developed ”. The same author described the structure of the Forest of Dean coalfield and noted the perfectconformity of the Dry brook Sandstone on the Whitehead Limestone and the overstep of theCoal-measures. The latest description of the sandstone, and the one which is most complete, is given by Dr. Sibly in his work on the ironstone of the Forest of Dean. His description reads “ Red, white, and mottled red and white sandstones compose the bulk of the formation. The rocks are mainly friable, but compact and even quartzitic rocks occur. In the north-east seams of quartz conglomerate are numerous. In the south-west bands of gritty limestone and dolomite develop ”.

THE finding of a small pebble of fine-grained quartz-dolerite in an exposure of the Upper Brockram in George Gill, near Appleby, by Professor Arthur Holmes in 1925 and its identification with the rock of the Whin Sill led to the direct establishment of the timeof injection of the Whin Sill and related dykes as post-Carboniferous and pre-Upper Brockram (1928, pp. 532–4). Since 1925 parties of students from the Durham Colleges’ Department of Geology have made each year a careful search for similar pebbles not only in the George Gill exposures but in a number of others in the Brackenber Moor neighbourhood. These efforts have not been rewarded with any success until the present year, when a party under my guidance made a thorough examination of the George Gill Brockram and Mr. A. R. Leathley, of Hatfield College, had the good fortune to hammer out a pebble of doleritic aspect.