3. Methods of Working.

The almost universal system of working is by bord-and-pillar, or the Scottish room-and-rance, whieh is very similar. Generally the pillars are left much too small, but sometimes the plan is properly laid out and n fair proportion recovered. The roofs vary very much: on the western coast of the South Island, hard gritty rock; in the Kaitangata mines, hard coarse conglomerate; at Kawnkawa, sandstone; in the Waikato and in many of the brown-coal-mines, running sand.

There are on the official list 161 coal-mines, but of these 20 are dormant, and the remaining 141 may be classified as below. In some parts of the official reports two or more pits are occasionally grouped, which accounts for the discrepancy noticeable between this table and that given on page 105.