The Supply and Waste of Coal. 323 



Let us now see what our calculation amounts to, and what 

 are the deductions that cause so much difference of opinion in 

 the estimates of intelligent men. With the same figures before 

 them different writers have come to conclusions so exceedingly 

 different that it is worth while to judge for ourselves. 



According to the table there are not less than 4500 square 

 miles of exposed coal measures in Great Britain, and at least 

 1500 square miles of country where coal may be worked with 

 profit beneath overlying formations. Now, if we assume that 

 the general average of total thickness of seams to be fifty feet, 

 which is probably not very wide of the mark, there will appear 

 to be a grand total of 6000 x 568,000 x 50 = 170,400,000,000 

 tons of coal. 



From what has been already said, the following deductions 

 must be made from this amount. 



In the estimated area is included the whole district on 

 which all the beds crop out, or are believed to exist under 

 cover. Very much of this is not available, and the actual 

 quantity depends on the dip of the bed, the faults, the depth of 

 the seams, and the mode in which the coal seams are dis- 

 tributed. Thus, in some large areas of coal measures there are 

 no workable seams whatever; in others the difficulty of 

 reaching them renders them valueless. A deduction of fifty 

 per cent, must probably be made on these various accounts, if 

 we would ascertain the available supply. 



In the estimated thickness the average is intentionally taken 

 low, but it includes all the workable seams. Now, it rarely 

 happens than more than two or three seams are got. The 

 others are more or less injured, or are for the time neglected, 

 and the resumption of workings in an old colliery to take other 

 seams, at first neglected, is known to be a most dangerous and 

 doubtful speculation. Thus it is practically the case that only 

 a part of the average workable thickness is ever obtained. 



Next comes the question of waste. It is impossible for 

 those who are not familiar with coal working to understand 

 how very large and serious a matter this is ; but the reader will 

 be prepared to recognize some of the causes. 



First : there is the waste from poor coal near the outcrop of 

 the beds. This is now unimportant, as few coals are worked 

 near the crop, but it is a considerable deduction from the esti- 

 mated quantity. Next : there is the deduction for bad coals near 

 and between faults. In this way large portions of a coal-field 

 are sometimes valueless, inasmuch as they do not pay for 

 working. Thirdly : there is waste from the mode of working. 

 A gallery, or drift, as it is called, is cut in the coal when 

 reached, and other drifts at right angles to this, leaving large 

 square columns, which are smaller or larger, according to the 



