THE BERING RIVER COAL FIELD 



429 



lish Company, and the Davis groups. On the Cunningham claims sev- 

 eral long tunnels have been run. At the McDonald mine on the Con- 

 troller Bay group is a working drift more than 600 feet long. On the 

 claims of the English Company there are three tunnels with a total 

 length of more than 900 feet. On the Davis group is a tunnel whose 

 length is more than 500 feet. During the summer of 1910 the Davis 

 group was the only one in the field upon which systematic develop- 

 ment work was being carried on. 



Looking Dowx Elk Creek. Haetlixe Claims. 



Summary axd Conclusions 

 The coals of the Bering Biver field are of good quality, and the 

 tonnage is unquestionably great. But the probable amount of this coal 

 which is available at present or will be available in the near future 

 can not be stated with any degree of reliability. The conditions of oc- 

 currence are such that until extensive development has revealed many 

 data at present unknown, an estimate of the available coal would be 

 little more than a guess. In coal fields of spmewhat simple structure 

 fairly reliable estimates may be made of the available coal from a 

 study of the outcrops, but in fields such as the Bering field, where the 

 structure is complex, such estimates are of little value, and in fact may 

 be harmful. The figures are likely to be overemphasized, and even 

 misused, by those who are endeavoring to interest the investing public. 

 In much of the Bering field the rocks are folded, faulted, jointed and 

 crushed ; the coal beds are known to vary much in thickness within 

 short distances along both the strike and the clip ; the coal beds in sev- 

 eral places may be seen to change somewhat abruptly into carbonaceous 

 shale, and in places they are intruded by igneous rocks. As yet, the 

 bods in the different parts of the field have not been correlated, nor is 



