A HISTORY OF LANCASHIRE land surface with sluggish rivers would thus account for the greater prevalence of shales and the feeble development of sandstones which mark the Middle Coal Measures. ■ . r u Similarly it has been held that the great development of grits and sandstones which form the Millstone Grit can only be accounted for by a general and rapid upheaval of the land surface at the close of the Pendleside period, by means of which rivers acquired greater velocity and destructive power, and were thus able to carry heavy loads of sand and pebbles from the land into the sea. The former wide extension of the Coal Measures over England, and their development over many parts of the continent of Europe, point unmistakably to the existence of vast tracts of alluvial land at this time, and these in turn were probably but the maritime plains of a huge continent whose inland surface was very mountainous, watered by a heavy rainfall, and drained by mighty rivers. The Upper Coal Measures, best seen in the neighbourhood of Manchester and along the southern borders of the Lancashire coalfield, difiFer markedly from the rest of the Carboniferous series in being made up mostly of red, green, and purple shales and clays, with thin limestones and sandstones. Coal seams only occur in the lower portion. The character of these deposits seems to indicate that the conditions we have already described were followed by the formation of freshwater lakes cut oflF from the sea and subject to evaporation. The limestones are such as would be formed by precipitation, whilst the prevalence of ferric oxide would seem to show that it was deposited as the sediments were formed, every grain being coated with it, a circumstance hardly likely to occur in sea-water or where the sea had access. As is evidenced to-day in many parts of the world, landlocked waters subject to evaporation are but little fitted to support life, and the deposits formed under similar conditions in Upper Coal Measure times show a great reduction in numbers as contrasted with the rest of the series, whilst, with the exception of the ostracods and Spirorhis, those species which persisted are found to be dwarfed and thin-shelled, whilst fish remains are rare. Considerable attention has been paid of late years to the palaeontology of the Carboniferous System and the occurrence of life zones, and it may be regarded as certain that the facts which are being collected will result in some modification of the existing and generally recognised sub- divisions. These at present are as follows : — f [ Upper. TT i-i 1. T I Coal Measures ( Middle. Upper Carboniferous < I r [ Millstone Grit Series. (Pendleside Group (' Yoredale Series '). Mountain or Scar Limestone. Lower Limestone Shale. THE CARBONIFEROUS OR MOUNTAIN LIMESTONE This lowest visible member of the series rises to the surface in North Lancashire, occupying a tract of country between Barrow in Furness, Dalton in Furness, and Ulverston, thence passing eastwards by a few outliers to Cartmel and Burton in Kendal, from which it trends south by Carnforth to near Morecambe. The rocks then dip to the south-east under the Millstone Grit country, rising again to the surface in the Forest of Bowland, or Bolland, and the Longridge Fells. From here they sweep round the Millstone Grit hills to the river Hodder, Whalley, and Clitheroe, where they form a strong anticline known as the ' Clitheroe Anticlinal.' To the south-east of Whalley and Clitheroe they dip from the anticlinal under the Pendle Range and the Burnley Coalfield, to again re-appear in the Todmorden and Hebden Bridge valleys over the Yorkshire border. The Carboniferous Limestone country is well marked, rising into bold hills along the flanks of which are majestic mural clifis or ' scars ' formed by the outcrop of the massively bedded limestone. Such ' scars ' are perhaps best seen in Derbyshire, but examples are not unfrequent in North Lancashire, in the Cartmel and Ulverston districts, in the Longridge Fells, and near Clitheroe, Whitewell, and Whalley. It will be perceived that the Carboniferous Limestone really forms two basin-shape de- pressions or troughs, with the Clitheroe Anticlinal between. The Carboniferous Limestone of the Furness and northern district is chiefly remarkable for the extensive deposits of haematite which occur in it, usually in the form of irregular masses and pockets.* At Clitheroe it consists of a lower black bituminous bed overlaid by shales containing FenestelltSy and a massive light-coloured limestone seen at Salt Hill and Coplow quarries, near Clitheroe, Worsaw Hill, and other places. The lower black limestone can be seen at Horrocksford quarries, the Bold Venture limeworks, and Tiviston ^ J. D. Kendall, The Iron Ores of Great Britain and Ireland (1893), pp. 54, 64. 6
