Launders should have high enough velocities to prevent particles from settling, or if they fall to the bottom, to keep them rolling and sliding. The depth of water should not be much over the diameter of the largest rolling particles. For concentrates and heavy gangues slopes should be increased 25—100%.

SPRAY WATER IN LAUNDERS:—While it is claimed that the quantity of water flowing with ore in a launder does not definitely follow Kutters formula, etc., the following data for the flow of water in a rectangular wooden launder will assist in calculating quantities of ore and water. Actual quantities in mill launders is probably between 50% and 75% of the quantities given below.

Launder Slopes.—In the absence of specific data, the launder slopes given in Table 37 should be used in laying out a flotation plant.