A Map of the Drift Geology of Great Britain and Northern Ireland

the whole of Ireland was published when the first geological survey was com? pleted (Geikie, A. 1910), but in Great Britain many of the Old Series sheets of the One-inch Geological map did not show the drift deposits. Although the New Series has been extended over a considerable area during this century, very many of the areas where the drift was not shown on the Old Series maps have not been re-surveyed by the Geological Survey. The main effort of the Geological Survey in recent years has been directed towards the re-mapping of areas with resources of economic value, particu? larly coal and ironstone. Unfortunately the main areas still lacking drift maps have no such resources and are likely to have a very low priority for survey. In recent years, the only appreciable addition to the published drift cover has been in the East Midlands, where maps covering the Jurassic ironstone areas have been published. In the absence of a complete cover of field survey the Geological Survey has been unable to publish a small-scale map of the drift geology of Great Britain. Maps of the solid geology are available, either at the 'io-mile' (1:625,000) scale in two sheets, (Geo? logical Survey, 1957) or in a single sheet at a scale of 25 miles to 1 inch (1:1,584,000). Maps at smaller scales are found in many atlases. The 25-mile map of the Geological Survey has recently been redrawn, and the new edition is an extremely attractive map (Geological Survey, 1959). For the geographer, as for anyone concerned with the land surface of this country, the map showing solid geology has considerable limitations. As may be seen from any collection of New Series One-inch maps, or from the few Quarter-inch sheets that are published in the 'drift* style (e.g. the Quarter-inch Drift Map, Sheet 12, Norfolk, 1953), much of the solid geology is deeply buried under these superficial deposits. Over some of the glaciated lowlands of this country these surface deposits are over 100 feet thick, and form a landscape independent of the solid rocks beneath. The areas that have not so far been surveyed in the field are fairly widely scattered, but include much of the upland areas of Scotland and Wales, and also parts of the Midlands and southern England. The fact that some areas are covered only by Old Series maps, surveyed some eighty or 100 years ago, is not a serious disadvantage. A major deficiency of these Old Series sheets is their very inadequate subdivision of the Palaeozoic rocks, but where they show drift deposits the accuracy of representation often comes very close to that achieved by the best modern sheets. In any case, the delimitation of drift boundaries is a very subjective matter; the particular criteria to be used and the minimum thickness of deposit to be mapped are difficult matters to decide.