SALTER — A CHRISTMAS LECTURE ON COAL. 



237 



hollow space left beneath these gave rise to the original figure of the 

 dome-shape of Stigmaria, and the idea of its being a floating plant, an 

 idea which has figured in a hundred essays on coal. It is an excellent 

 proof how much our logic may go astray with the premises wrong. 



Lastly, as a conclusive proof of the marine nature of coal, the presence 

 of very salt sea- water in it, containing iodine and bromine, might have 

 been, and should have been, adduced. 



In p. 13, the printers or I have called paper coal " dysoile", instead 

 of dijsodile. 



In p. 183, I am made to say that plants give out less carbonic 

 acid at night than they take in (by day). The words in brackets 

 should not be left out. 



But if I attempted to fill up all my own omissions I should fill this 

 number. The greatest fault of all is to have talked in p. 13 of finishing 

 in the next number or so, and then extend over half the year. 



A subject of such vital national importance ; a traffic which employs 

 directly half a million of our countrymen; and whose yearly value, 

 as raw or manufactured material, represents such enormous capital, 

 cannot be a subject of indifference to any man. 



The question whether we can afford to go on digging away at the 

 present rate, or even a greater one, and exporting to other nations as 

 well as keeping up our own steam, has been already answered by my 

 friend, Mr. Hull, in his excellent little book, " The Coal-Fields of 

 Great Britain."* His results are summed up in the last page, and 

 may be briefly given. 



" 1. There is coal, at various depths, over much larger areas than 

 our maps give, down to depths of nine thousand or ten thousand feet, 

 of which we are never likely to reach more than four thousand feet, 

 from increase of temperature. 



" 2. There is a supply of coal within the smaller limit enough to 

 afford sixty million tons a year for ten centuries." 



When our coal-fields are being exhausted, then the grand untouched 

 deposits of America will come into play. Let us get out all we can ; 

 distribute it as widely as the arts of peace require ; use it as care- 

 fully as such a blessing should be used, and do all the good with it 

 we may. 



1861 : Stamford, Charing Cross. A new edition is in the press. 



