In proportion as the cuts a, of the first story E F, are thus filled up, the greater part of the timbering is withdrawn, and made use of elsewhere. The intermediate cuts b, c, b, are next mined in like manner, either beginning with the cuts c, or the cuts b, according to the localities. From [fig. 729.] it appears that the working may be so arranged, that in case of necessity, there may be always between two cuts in activity the distance of three cuts, either not made, or filled up with rubbish. Hence, all the portion of the bed of ore may be removed, which corresponds to a first story E F [fig. 730.], and this portion is replaced by rubbish.
The exploration of the upper stories E′ F′, E2 F2, E3 F3, is now prepared in a similar manner; with which view shafts h h3, k k3, are formed from below upwards in the wall m of the deposit, and from these shafts oblong galleries proceed, established successively on a level with the stories thus raised over one another. See [fig. 730.] The following objects may be specified in the figures:—
a a, the first cuts filled up with rubbish, upon the first story E F, [fig. 729.]
b b, other cuts subsequently filled up, upon the same story.
c, the cut actually working.
d, the front of the cut, or place of actual excavation of the mineral deposit.
e, masses of the barren rock, reserved in the cutting, as pillars of safety.
f, galleries, by means of which the workmen may turn round the mass e, in order to form, in the roof t, an excavation in the direction of the deposit.