Troughs and basins in the middle of the ocean, (2) the steeply sloping ridge which interposes a narrower barrier between two depressions, and (3) the plateau or wide elevation rising steeply on all sides from a depression.
In diameter, leaves the stamps in suspension in water, and passes through a series of troughs in which the heavier mineral is collected; this then passes through a series of washing operations, which leaves a mixture consisting chiefly of tinstone and arsenical pyrites, which is calcined and washed again, until finally black tin containing about 60 to 65% of metal is left.
They are shallow troughs about 12 ft.
In these troughs the depth is seldom much less than 3000 fathoms, and this is exceeded in a series of patches to which Murray has given the name of "Deeps."
Maximum), as distinct from the long, narrow and deep troughs occupied by the other chief lakes, which average from 40 to 135 ft.