If all sizes of material produced by a forest are salable, very little logging debris of slash remains to hinder the reproduction or to increase the fire hazard. In the white-pine type of northern Idaho, however, only the larger and most valuable forest products can at present be taken out at a profit. The virgin forests of this region yield from 15,000 to 40,000, and often 50,000, board feet per acre. They usually contain many fallen dead trees. Much material, in the form of branches, tops, and swamped undergrowth, is left after a logging operation. This debris may cover from 40 to 90 per cent of the forest floor and average from 1 to 3 feet deep. The uncut forest is shown in Figures 1 and 2 and logging waste in Figures 2 and 7.