206 SCIENCE IN SHORT CHAPTERS. 



effort would here be necessary, and if anybody doubts 

 whether Englishmen could be found to make the effort, let 

 him witness a " pot-setting" at a glass-house. Negro labor 

 might be obtained if required, but my experience among 

 English workmen leads me to believe that they will never 

 allow negroes or any others to beat them at home in any 

 kind of work where the wages paid are proportionate to the 

 effort demanded. 



If I am right in the above estimates of working possi- 

 bilities, our coal resources may be increased by about forty 

 thousand millions of tons beyond the estimate of the Com- 

 missioners. To obtain such an additional quantity will 

 certainly be worth an effort, and unless we suffer a far worse 

 calamity than the loss of all our minerals, viz., a deteriora- 

 tion of British energy, the effort will assuredly be made. 



I have said repeatedly that it is not physical difficulties 

 but market value that will determine the limits of our coal- 

 mining. This, like all other values, is of course determined 

 by the relation between demand and supply. Fuel being 

 one of the absolute necessaries of life, the demand for it 

 must continue so long as the conditions of human existence 

 remain as at present, and the outer limits of the possible 

 value of coal will be determined by that of the next cheapest 

 kind of fuel which is capable of superseding it. 



We begin by working the best and most accessible 

 seams, and whije those remain in abundance the average 

 value of coal will be determined by the cost of producing it 

 under these easy conditions. Directly these most accessible 

 seams cease to supply the whole demand, the market value 

 rises until it becomes sufficient to cover the cost of work- 

 ing the less accessible; and the average value will be 

 regulated not by the cost of working what remains of the 

 first or easy mines, but by that of working the most difficult 

 that must be worked in order to meet the demand. This is 

 a simple case falling under the well-established economic 

 law, that the natural or cost value of any commodity is 

 determined by the cost value of the most costly portion of 

 it. Thus, the only condition under which we can proceed 

 to sink deeper and" deeper, is a demand of sufficient energy 

 to keep pace with the continually increasing cost of pro'- 



