A glossary of mining and metallurgical terms

72 A GLOSSARY OF MINING AND METALLURGICAL TERMS.
whereby copper (and nickel) are concentrated in the interior of the
lumps.
Roadiag ami reaction process. The treatment of galena in a
reverberatory, by first partially roasting at a low temperature, and
then partially fusing the charge at a higher temperature, which
causes a reaction between the lead-oxide formed by roasting and the
remaining sulphide, producing sulphurous acid and metallic lead.
Roasting and reduction proceaH. The treatment of lead ores by
roasting to form lead-oxide, and subsequent reducing fusion in a
shaft-furnace.
Rob. To extract pillars previously left for support; or, in gen-
eral, to take out ore or coal from a mine with a view to immedi-
ate product, and not to subsequent working.
Rock-breaker. -Usually applied to a class of machines, of which
Blake's rock-breaker is the type, and in which the rock is crushed
between two jaws, both movable, or one fixed and one movable. It
is common to use a rock-breaker instead of haud-spalling to prepare
ore for further crushing in the stamp-mill.
Rock-drill. A machine for boring in rock, either by percussion,
effected by reciprocating motion, or abrasion, effected by rotary mo-
tion. Compressed air is the usual motive power, but steam also is
used. The Burleigh, Haupt, Ingersoll, Wood, and other machines
operate percussively ;
the diamond drill (which see) abrasively.
Rocker. A short troui>:h in which auriferous sands are agitated
by oscillation, in water, to collect their gold.
Rod-tools. See Pole-tools.
Rolley. A large truck carrying two corves.
Rollctf-icai/. A gangway.
Rolling. See Roll-train.
Rolls. 1. Cylinders of iron or steel revolving towards each other,
between which rock is made to pass, in order to crush it. 2. See
Roll- train.
Roll-train. The set of plain or grooved rolls through which iron
or steel piles, ingots, blooms, or billets are passed, to be rolled into
various shapes.
Rondle or Rondellc. The crust or scale which forms upon the sur-
face of molten metal in cooling.
Roof. The rock overlying a bed or flat vein.
Roofing. The wedging of a loaded wagon or horse against the
top of an underground passage.
Room, Scot. See Breast and Post-and-stall.