These are exceedingly reliable. Measurements were taken by the Forest Service of practically pure fir on about 400 areas in thirty-five different age stands from 10 to 140 years old, ranging along the western Cascade foothills from the Canadian line to central Oregon. Since reforestation investment is likely to be confined mainly to the more promising opportunities, only such growth was measured as gave an average representation of the better class of the two should all the general territory covered be graded in two quality classes of all around ability to produce forests. On the other hand, care was taken not to represent the maximum of the better class, data being taken only from permanent forest land and not from rich potential agricultural land which might show unfairly rapid forest growth. The average areas were actually measured and the number, age, form, diameter growth, height growth, board foot contents, etc., of all the trees on them were accurately determined. Trees 12 inches in diameter 4-1/2 feet from the ground were considered merchantable, and it was assumed they could be used to 8 inches in the top. From this data were prepared tables and diagrams showing the average development of trees and stands under fairly favorable conditions in the region west of the Cascades. This gave the following yield per acre: Age of Stand. Feet, B. M. Age of Stand. Feet, B. M. 40 12,400 90 70,200 50 28,000 100 79,800 60 41,000 110 90,300 70 51,700 120 101,500 80 61,100 130 113,000 Let us see how these figures can be used in answering the primary question of the prospective timber-grower: "Will it pay to hold my cut-over land for a second crop?" Obviously no certain answer can be printed here, not only because no uniform stumpage prices or carrying charges can be predicted but also because individuals may differ as to what profit is necessary to make the investment "pay," so it will be necessary to analyze the situation so each may select the premises which suit his own case and judgment. The investment made by the holder of cut-over land is of two kinds; that represented by the land which otherwise he might sell, putting the proceeds at work in some other business, and the annual carrying charges which otherwise he might also invest differently. The sum obtainable by investing the money available by sale after logging, adding to it yearly the sum required for fire prevention and taxes, and compounding both at a satisfactory interest for the entire period, is practically the cost of holding the tract for any given number of years. By calculating this cost upon a basis of one acre, and dividing it by the yield board measure which the same period will produce, the cost per thousand feet of growing a second crop is arrived at.