394 MR ROBERT KIDSTON ON THE FOSSIL PLANTS IN THE 



flaggy sandstones, and two or three thin beds of coal. To the south of Pimbo Lane is 

 Billinge Hill, where there are quarries in the sandstone near the Beacon, which is on the 

 highest ground, 593 feet above Ordnance datum. Probably, in consequence of the 

 predominating sandstones, the subdivision forms an elevated district, and good sections of 

 the strata are of frequent occurrence. In the Geology of Wig an* Professor Hull 

 gives a section through the Lower Coal Measures at Billinge, which shows the thickness 

 of the successive beds, and that they are altogether 1881 feet thick. There are six beds 

 of coal, the Upper Mountain Mine being 2 feet, and the Loiver Mountain Mine being 2 

 feet 8 inches thick, with four intermediate seams, much too thin to be worked. In a 

 sandstone quarry near the top of Billinge Hill, Catamites J Bothrodendron, and Lepido- 

 dendron have been found. 



Middle or Productive Coal Measures. 



The Middle Coal Measures form the most important subdivision, economically 

 considered, for they contain all the valuable beds of coal. They extend from near 

 Huyton and south of St Helens, many miles to the north-east, forming two projections, 

 bounded on each side by the Trias, a few miles to the east of Liverpool. Although there 

 are many quarries and small exposures where they may be seen, there is no important 

 section showing a great thickness of the beds and the relative position of the various 

 shales, sandstones, and coal seams. The whole of the strata between the Lyon's Del/ 

 Coal at the top, and the Little Delf Coal or Arley Mine at the bottom, are considered 

 to constitute the subdivision. 



The Middle Coal Measures at Prescot are the nearest to Liverpool, and may be adopted 

 as a scale for comparison with those at St Helens and Wigan, and the coal seams at each 

 of these places have been correlated with those on the same horizon, though they are 

 usually known by different names, which were originally given to them before it was 

 possible to ascertain their relative position in the Coal Field. The following General 

 Section, compiled from the Geological Survey Memoirs, is the final result of observa- 

 tions extending over many years. 



The section given on the opposite page shows that the Middle Coal Measures are 

 thinner at Prescot than at St Helens, where the coal seams are at greater distances 

 from each other, while at Wigan there is a still greater expansion of the series. It also 

 shows the equivalent of each coal seam at Prescot, St Helens, and Wigan ; as, for 

 example, that the Tenlands Coal at Prescot becomes the Ravenhead Coals at St Helens, 

 and the Wigan 5-feet Mine at Wigan ; and that the Little Delf Coal at the two former 

 places becomes the Arley Mine, or Orrell 4-feet at the latter place. The succession of 

 the coal seams could only have been ascertained from the records obtained in sinking 



* Memoirs of the Geological Survey. 



t The Liverpool Museum contains specimens of Calamites Suckowii and Bothrodendron (decorticated) from this locality. 

 -R. K. 



