THE NATIONAL GEOGRAPHIC MAGAZINE 



429 



EQUIPPED FOR RESCUE WORK IN 



Photograph from U. S. Bureau of Mines 

 COAE-MINE DISASTERS. 



It would be difficult to overestimate the value of the work of the United States Bureau 

 of Mines in the improvement of methods for the prevention of mine disasters and in rescue 

 operations in the accidents that, in spite of every precaution, still occur. Modern appliances 

 and quick mobilization of rescue forces have saved thousands of lives in the industry. 



aginable supplies of carbonic acid gas, 

 which was inhaled by the Brobdingnagian 

 jungle. 



Indeed, so rich was the atmosphere in 

 its supply of this gas that while it made 

 vegetation grow extraordinarily rank it 

 would have suffocated man. Further- 

 more, there -was warmth exceeding any- 

 thing we know in the tropics today, and 

 there was moisture in abundance— more 

 than the most spendthrift of plants could 

 wish for. 



The vegetation of that time was not 

 limited by zones, neither by continents. 

 In the coal beds of Alaska, in the meas- 

 ures of the Antarctic, or in the mines of 

 Australia, Europe, Asia, or America — in 

 them all one finds evidences that the five 

 hundred specimens of plants of that era, 

 preserved by Nature for our inspection, 

 acknowledged no climatic zone nor found 

 themselves limited by any ocean. 



How amazingly dense was the vegeta- 

 tion of the coal-forming era may be 

 shown by comparisons with existing for- 

 ests. The densest jungle I have ever seen 

 is that lying along the Motago River, in 

 Guatemala, and men who have traveled in 

 every tropical land of the earth say that 



they have never seen anything surpass- 

 ing it. 



Should Nature, by the processes of the 

 coal age transform that jungle into a coal 

 seam, it would be only a few inches thick ; 

 yet there are coal seams existing today 

 which are sixty feet thick, though ten feet 

 is regarded as a fine seam, and three feet 

 will produce more than five thousand tons 

 to the acre. 



THE EAMIEV-TREE OE COAL 



It is interesting in passing to note the 

 family-tree of coal. Wood contains some 

 50 per cent of carbon. As dense forests 

 have decayed they have left peat beds 

 behind them. Subjected to the pressure 

 of superincumbent strata, and touched 

 slightly with the internal heat of the 

 earth, peat becomes lignite, and we can 

 see peat so near to being lignite and lig- 

 nite so near to being peat that the line of 

 demarcation is hard to draw. 



After lignite comes cannel coal, the 

 connecting link between lignite and bi- 

 tuminous coal. Bituminous coal contains 

 approximately 88 per cent of carbon as 

 compared with 67 per cent in lignite and 

 84 per cent in cannel coal. Anthracite 



