Revieivs — HiiU's Coal-fields of Great Britain. 83 



Coal below two feet in thickness should not be calculated in estimat- 

 ing our future Coal resources. In this we agree with Mr. Hull. 



The presumable quantity of Coal yet to be worked in Great Britain 

 and Ireland, after necessary deductions, and at a depth not exceeding 

 4000 feet, is 



In visible Coal-fields 79,752,000,000 



In concealed Coal-measures 66,273,000,000 



Total tons 136,025,000,000 



"a supply," adds Prof. Hull, "which, if drawn upon at the rate of 

 one hundred and thirty millions of tons, the quantity of 1878, would 

 be sufficient to last for more than a thousand years." 



The annual production of Coal over the whole globe is now said 

 to be two hundred and eighty-nine millions of tons per annum. 

 Under this heading the quantities have been brought up to dates 

 varying from 1873 to 1879 for the various countries. During the 

 past four years (1876-1879) the increase in output in our own country 

 has been practically stationary. That for 1879 amounted to 

 134,008,228 million tons. In the chapter on concealed Coal-fields 

 an account of the recent important borings in the S.E. of England 

 has been added, especially those of the London area. Prof. Hull 

 considers that, " we must look to tracts lying south of the Thames 

 Valley as the possible area of concealed coal-fields," in the South-east 

 of England, and especially, as Mr. Godwin-Austen has pointed out, 

 along the margin of the North Downs, and the borders of the 

 Wealden area. 



We are glad to see that Prof. Hull, where practicable, devotes a 

 few pages to the organic remains of the various Coal-fields under 

 description. The occurrence of marine bands of fossils is always 

 strongly dwelt on, and plays an important part in the classification 

 adopted throughout the work. As a remarkable instance of the 

 persistence of a calcareous stratum over large areas, is cited the 

 Spirorhis limestone of the Upper Coal-measures, which can be traced 

 in the same position throughout the Coal-fields of Coalbrook Dale, 

 and Forest of Wyre southward, through Lancashire northward, and 

 Warwickshire eastward, representing an area of about 10,000 square 

 miles, and is only on an average about one foot in thickness. 



The descriptive portions of the various Coal-fields have not been 

 greatly altered, or added to, and remain nearly the same as in 

 the last edition, excepting, of course, the information relating to 

 quantities won and still to be wrought. 



In the chapter devoted to the Coal -fields of Europe, a useful table 

 is introduced, showing the corresponding groups throughout the 

 British Islands and the various Continental Coal-basins. It appears 

 that the uppermost division of the Coal-measures is usually absent 

 from the latter. In the South Staffordshire Coal-field the great ten- 

 yard, or "Thick Coal," has been either worked out, drowned, or 

 destroyed to such an extent that probably little more than one-tenth 

 remains to be won. Professor Hull wisely suggests that the coal 

 proprietors of the district should combine to uu water this large area. 



