BOOK V.

125

thickness, and high enough that their ends, which are cut square, almosttouch the top of the tunnel; then upon them is placed a smaller dressed cap,which is mortised into the heads of the posts ; at the bottom, other smalltimbers, whose ends are similarly squared, are mortised into the posts. Ateach interval of one and a half fathoms, one of these sets is erected ; each oneof these the miners call a “ little doorway,” because it opens a certain amountof passage way ; and indeed, when necessity requires it, doors are fixed to thetimbers of each little doorway so that it can be closed. Then lagging ofplanks or of poles is placed upon the caps lengthwise, so as to reach from oneset of timbers to another, and is laid along the sides, in case some portion ofthe body of the mountain may fall, and by its bulk impede passage or crushpersons coming in or out. Moreover, to make the timbers remain stationary,wooden pegs are driven between them and the sides of the tunnel. Lastly,if rock or earth are carried out in wheelbarrows, planks joined together arelaid upon the sills ; if the rock is hauled out in trucks, then two timbersthree-quarters of a foot thick and wide are laid on the sills, and, where theyjoin, these are usually hollowed out so that in the hollow, as in a road, the ironpin of the truck may be pushed along ; indeed, because of this pin in thegroove, the truck does not leave the worn track to the left or right. Beneaththe sills are the drains through which the water flows away.

A —Posts. B—Caps. C—Sills. D —Doors. E —Lagging. F —Drains.

11 B

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Miners timber drifts in the same way as tunnels. These do not, however,require sill-pieces, or drains ; for the broken rock is not hauled very far, nor doesthe water have far to flow. If the vein above is metal-bearing, as it sometimes is