128 Coal-measures. 



alternations are of constant occurrence. In some cases 

 in East Lothian, beds of fireclay, with Stigmaria, and 

 thin layers of coal lying on old terrestrial soils, im- 

 mediately underlie marine limestones with Productas. 

 In the Dalkeith coal-field valuable beds of coal with 

 shales, &c. are interstratified with a thick series of beds 

 of Carboniferous Limestone. The Burdiehouse brackish 

 water limestone in East Lothian is the lowest of the 

 limestones, and yields many small bivalve Crustacea 

 of the genus Estheria, besides fish of the genera Mega- 

 licthys and Holoptychius. 



In the East and Mid Lothian coal-fields about 

 20 beds of workable coal occur, besides many smaller 

 layers. Eleven workable beds of coal are known 

 above the Millstone grit or Moor rock, and 17 asso- 

 ciated with the Carboniferous Limestone beds below 

 the Millstone grit. The Carboniferous strata of the 

 Lothians cross the Firth of Forth beneath the sea, and 

 form great part of Kinross and Fife, where there are 

 29 workable beds, one of which is 21 feet, and others 

 from 5 to 9 feet in thickness. The western part of 

 the basin in Lanarkshire and Ayrshire yields 8 

 or 10 workable coal seams. It is in these districts 

 that the well-known black-band ironstones occur. 



I have already said that the South Wales, Dean 

 Forest, Bristol and Devonshire Carboniferous areas 

 originally formed one, and have been separated by 

 disturbance of the strata and subsequent denudation. 

 The same kind of original continuity may be inferred 

 concerning all the coal-fields of the middle of England, 

 North Wales, and northward to Cumberland and North- 

 umberland, and the latter was even probably joined to 

 the great coal-field of central Scotland. After the 

 close of the Carboniferous epoch, this large area was 



