HOLMES] ABORIGINAL OPERATIONS IN AN IRON MINE 
505 
pockets and seams of soft red and yellow oxides, and in places there 
were irregular openings and partially filled cavities. Two of these 
openings are shown in plate l, a view of the face of the mine taken 
by Mr Clark McAdams of St Louis. The miners would drill with 
great difficulty through the hardest of ore, to have the drill drop sud¬ 
denly into a cavity of unknown depth. It was difficult to discover 
just which of these openings and cavities were artificial, or whether 
or not they had been penetrated by the ancient workers, as changes 
Fig. 30.— Section indicating the manner in which the galleries or borings penetrate 
the ore-body, (a, a , Surface traces of ancient pits. <$, Ore-body, c, Filling of excava¬ 
tions. d, Borings of the ancient miners, e, Floor of mine.) 
are constantly taking place in such ore-bodies. Percolating waters 
fill up or clear out the passage-ways. Generally, however, as the 
walls were broken down the openings were found to connect with 
the superficial pittings, as indicated in figure 30. 
It appears certain that the larger openings and tunnels in which 
the sledges were found had been opened up or enlarged by the 
ancient miners, and that in the search for other bodies of the de¬ 
sired product they had followed weak lines and partially filled pas¬ 
sage-ways, removing the projecting masses of hard ore, where these 
