page 334 note 1 Specimens of the sand and clay from the two deposits left by the Flood were submitted to the Petrographical Department of the Geological Survey, Jermyn Street, for microscopic analysis. Dr. H. H. Thomas's report was as follows:
‘The soil specimens and silts have been examined and I find Specimen Z is a fine grained, closely laminated silt, the laminae showing definite current-bedding and grading of particles. On a cross-section certain laminae may be seen to wedge out in a manner that can only be accounted for by the action of gentle currents. In a distance of two inches the laminae may tail off from a thickness of one or two millimetres to the merest film. The average thickness of the laminae is something less than a millimetre. The silt has a definite parting parallel to the surfaces of the laminae, which are seen to be covered with the minutest scales of detrital mica.
‘In constitution the material is mainly fine angular quartz with much finely divided mica, fairly abundant green hornblende with some augite and magnetite. The particles are somewhat variable in size, as would be suggested by the lamination of the sediment. They range up to 0·1 mm. but mostly they have much smaller dimensions.
‘Sample X. Has practically the same constitution and texture as Zexcept for the absence of lamination.
‘Sample y. A fine clay material with particles mainly under 0·01 mm. and highly micaceous. It is quite possibly water deposited, for it would be difficult to account for it in any other way.
‘The absence of lamellation might suggest wind-blown dust, but there is a complete absence of any larger or rounded particles which usually occur in aeolian deposits.
‘The material of X and Y appears to be derived in part from a series of bornblendic and augitic igneous rocks.’
Samples Z and Y are from the pit excavated this year, X from the shaft sunk in1928-9.
