Chat. XXYI.] thick ohe-baxd ox low geottnd. 559 
00° (vertical). In either case it would probably be better to open up the 
Fig. 32. — Quarrying a thick ore-band cropping out on low ground. 
deposit as a quarry, with stepped sides as indicated in the figure, the 
stepped lines indicating the approximate positions of the sides of the 
quarries for different depths. The difference introduced by the different 
angles of dip is that with a shallow dip more ore can be won down to a 
given depth than with a steep dip, the most favourable condition as 
regards dip being the one in which the ore-band is folded so as to be 
kept at the surface for a considerable distance across the strike, as at 
Kaihdongri (Plate 19). The depth to which such an open quarry could 
be carried, supposing the ore to continue, depends on a variety of condi- 
tions, of which the chief is probably the character of the ' country ' or 
waU-rock of the deposit. It might conceivably be carried to a depth 
of 150 to 200 feet ; but it is probable that before this, except under 
exceptional circumstances, such as great thickness of the ore -band, 
accompanied by very high quality, it would pay better to start mining the 
deposit, by the ordinary methods apphcable to veins. It will be seen that 
if worked as illustrated in figure .30 in the case of a hiU deposit, or as in 
figure 32 in the case of a plains deposit, the side of the quarry on the 
foot-wall side would keep moderately close to the foot-wall side of the 
deposit. In these cases it would be as weU to drive one or two tunnels 
into the foot- wall side in order to ascertain whether a second ore-band 
be present, as might easily be the case, and as is illustrated in 
figure .32. Or of course the same could be tested by boring. 
In the case illustrated in figure .33, in which the ore-band is supposed 
to be only 6 feet thick, and to crop out on low 
out on low ground!*^^'"" ground, there is little doubt that if the deposit 
continue to any considerable depth, and it be 
