242 



NA TURE 



[Jan. 15, 1885 



on the continent for some jewelled watches? : — A is the shape of 

 the visible dial ; c is the minute hand; n is the second-hand 

 (sometimes di:>pensed with) ; E is an aperture in the dial through 

 which is seen the hour, brought there by the hourly revolution 

 of the wheel B ; u is a wheel (and in watches of the size of a 



shilling a series of wheels or a metallic band rolling round a 

 drum of special construction for those liny watches) immediately 

 under the dial, set in motion once every hour, and bringing the 

 corresponding numbers under the aperture E. Chatei. 



Jersey, January 5 



THE COAL QUESTION 



IT is generally admitted that the amount of coal existing 

 below Great Britain at such depths that it can be 

 worked is limited, that large quantities of coal are annually 

 used, and that even the partial exhaustion of the fields, 

 accompanied, as it must be, by a rise in price, would 

 seriously affect almost all our manufactures, and greatly 

 endanger our commercial supremacy. But if we attempt 

 to go further, and say how long our supply of coal will 

 last, we meet with very different estimates. Nearly a 

 hundred years ago the question was discussed by Mr. 

 John Williams, and though the insufficiency of the data 

 did not allow him to give a definite answer, he at least 

 showed the vital importance of the subject. 



In 1861, Mr. Hull, by taking into account the area of all 

 our coal-fields and the thickness of the workable seams, 

 calculated that the total available coal in Great Britain 

 was 79,845,000,000 tons; this result was shown by a 

 second calculation to be slightly too low. Further, he 

 assumed that the output of coal, which was then 86,000,000 

 tons, could not rise much above 100,000,000, and there- 

 fore that our supply was sufficient for eight centuries. 



Four years later Prof. Stanley Jevons, in an admirable 

 essay on " The Coal Question," accepted the more impor- 

 tant of Mr. Hull's data, but showed that they would bear 

 a very different interpretation, and that, instead of the 

 eight centuries spoken of by Mr. Hull, "rather more than 

 a century of our present progress would exhaust our mines 

 to the depth of 4000 feet." He then shows th.it tin 

 absolute physical exhaustion of the fields is improbable, 

 but that before the twentieth century is far advanced the 

 output of coal will probably be checked by a rise in price 

 so considerable that England will be unable to compete 

 in manufactures with other nations still enjoying the pro- 

 fusion of C"al to which her present commercial prosperity 

 is so greatly due. These theories and results were re- 

 viewed and strengthened by Prof. Marshall in 1878 ("Coal, 

 its History and Uses"), with the aid of more recent 

 statistics ; and the present paper is intended to give a 

 short and simple account of the present state of the 

 question from the physical side, with the omission of the 

 more difficult and dubious arguments which may be 

 drawn from Political Economy. 



The arguments of Prof. Stanley Jevons were so con- 

 clusive, and his results so alarming, that a Royal Com- 

 mission, of which the Duke of Argyll was chairman, was 

 appointed, in 1866, to investigate the probable quantity of 

 coal contained in the coal-fields of Great Britain. In 

 1S71 the Commission reported that the coal-fields already 



in use still contained 90,207,000,000 tons of coal, and that 

 concealed coal-fields as yet unopened, near Doncaster, Bir- 

 mingham, and elsewhere, probably contained 56,27 3,000,000 

 tons more, or that, in all, 146,480,000,000 tons of coal were 

 available. Since that time about 1,780,000,000 tons of 

 coal have been raised, leaving as the available supply in 

 1884 about 144,700,000,000 tons. Subsequent investiga- 

 tions show that this estimate is probably considerablv too 

 high. 



These results were intended to include all beds a foot 

 and upwards in thickness lying within 4000 feet of the 

 surface, though it was rendered probable at the same 

 time that the amount of coal below 4000 feet is not very 

 large. The reason for excluding all beds less than a foot 

 thick is that, at present prices, it is found unprofitable to 

 work them, and hence, except in a few special cases, they 

 are left untouched, though rendered worthless for the future 

 from the disturbance of the strata occasioned by working 

 the other beds. 



Though we may assign no limit below which it is im- 

 possible to work, the cost of mining increases so rapidly 

 with increased depth that the price of coal must rise very 

 seriously before even the 4000-foot limit can be reached. 

 This increase of cost depends upon various causes. The 

 mere sinking of three shafts like those of Murton, which 

 are said to have cost 300,000/., burdens the undertaking, 

 if it last fifty years, with an interest and sinking fund at 

 4 per cent, amounting to 13,965/. per annum. More power- 

 ful winding and pumping engines must be employed, and 

 from the great expense of shaft- sinking, larger areas must 

 be worked from one shaft, necessitating extra expense in 

 underground haulage, ventilation, and supports. Further, 

 each actual coal-hewer requires a larger amount of assist- 

 ance to secure his safety and to remove his winnings in a 

 deep pit. A coal-hewer working at an open seam on the 

 surface of the ground would only require one labourer to 

 wheel away the coal, while in a deep mine each hewer 

 requires about three men to attend to the removal of the 

 coal, the pumping, and ventilation. 



The high temperature of the rock at great depths is 

 al an important factor in the expense of deep mining. 

 In England there is found to be a uniform temperature 

 of 50° F. about 5c feet below the surface ; but this temper- 

 ature is found to increase I 3 F. for every 60 feet descended, 

 so that at 4000 feet the temperature of the rock will be' 

 about 1 16 F. And though this temperature is not suffi- 

 ciently high to prevent working, and might be lowered a 

 few degrees by ventilation, it will cause a considerable 

 increase in the expense, both from the lassitude and extra 

 pay of the men, and the larger amount of air required, 

 which even now at Hetton amounts to 450.000 cubic feet 

 per minute. 



These difficulties account for the manifest reluctance 

 to sink deep pits, for the high price charged for the coal 

 from them, and for the fact that the 4000-foot limit has 

 not yet been approached. In 1846 the Messrs. Pemberton's 

 pit at Monkwearmouth reached 1720 feet; in 185S the 

 Astley pit at Dukinfield reached 2100 feet; in 1869 the 

 Rosebridge pit at Wigan reached 2448 feet ; in 188 1 the 

 Ashton Moss pit near Manchester reached 26S8 feet ; and 

 though the Lambert pit in Belgium has been worked at 

 ,1' > feet, the circumstances were exceptional, and it is 

 certain that the commercial success of such a pit in 

 England would necessitate a price of coal far higher than 

 it at present is. 



The early estimates of the annual output of coal are so 

 unreliable that it is useless to go back further than 1854, 

 when "Mineral Statistics " were first carefully collected 

 by Mr. Robert Hunt, and even in these returns the 

 amounts for the first few years are possibly as much as 

 three per cent, too low, from the difficulties of overcoming 

 the fears of the coal-owners as to the uses which might be 

 made of them. These returns have been collected and 

 arranged by Mr. Meade, in his "Coal and Iron Industries. 



