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MR ROBERT KIDSTON ON THE FOSSIL PLANTS IN THE 



the Harrock Hills, as shown on the maps of the Geological Survey. The general succession 

 of the Coal Measures shows the following subdivisions in the neighbourhood of Prescot, 

 St Helens, and Wigan : — 



Upper Coal Measures. 



Middle or Productive Coal Measures. 



Lower Coal Measures. 



The Lower Coal Measures contain a greater proportion of sandstone strata than the 

 other two subdivisions, and form the highest and most conspicuous ground; the Middle 

 or Productive Coal Measures contain nearly all the coal seams that are of sufficient 

 thickness to be worth working ; while the Upper Coal Measures are of little economic 

 importance. These subdivisions are principally the result of observations by Professor 

 Edward Hull, F.R.S., who originally surveyed the district for the Geological Survey 

 thirty years ago, though it had been described long before by the late Mr E. W. Binney, 

 F.R.S., to whom geologists are so much indebted for his valuable and long-continued 

 researches in the Lancashire Coal Field. The succession of the coal seams and the 

 thickness of the strata between them have been known for a long period, this information 

 having been gradually obtained from the sinking of shafts and working the coals during 

 the last one hundred years, but some of the most reliable details are given in the 

 " Sections of Shafts sunk in the Middle Coal Measures of Prescot, St Helens, Wigan, and 

 Burnley," by Messrs C. E. de Rance, F.G.S., and A, Strahan, B.A., F.G.S., published 

 by the Geological Survey. 



Railway Station. 



Prescot. 



Upper. 



Middle. Lower. 



Fig. 1.— Section through the Coal Measures at Prescot. 



The above section (fig. 1) along four miles of country from north to south, with 

 Prescot in the centre, exhibits in regular sequence the nearest development of the Coal 

 Measures in the country around Liverpool, and shows the subdivisions described. This 

 threefold succession is common to the whole of the Lancashire Coal Field, which was all 

 formed under the same general conditions, but it has been since broken up by faults, and 

 denuded to such an extent that the subdivisions appear at the surface in separate areas, 

 and the whole is frequently covered by the overlying Triassic strata which extend over a 

 large portion of Lancashire and Cheshire. 



