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%0 COAL MINES or

CHAPTER IV.

The Second , or Sunderland and, NewcastleCoal Formation. — Third, or MagnesianLimestone Formation—and Dykes.

The second, or Sunderland and Newcastlecoal formation is supposed to be about fifteenmiles by twenty, making a superficial area of300 miles, each mile containing about 4,645,000cubic yards, or tons, (as each cubic yard iscalculated to contain one ton of coal:) of thisfrom one fourth to one sixth is appropriated topillars and walls for supporting the mine, andthe annual consumption amounts to about3,100,000 tons.

The third formation is the magnesian lime-stone, which is found with different variationsall along the coast of Durham, breaking offat the Tyne. It is intercepted for abouttwenty miles on the coast of Northumberlandby the coal formation, and is only found invery inconsiderable quantities to the north. Itsprincipal range is from Teignmouth to Durhamand Hartlepool; and although the exact depth"