REVIEWS 685 



where it was carried out under the Department of Agriculture and 

 Technical Instruction for Ireland. Uniformity in the various countries 

 was further secured by conferences between the officers concerned. 



The work w^as carried out by women assistants under the supervision 

 of trained forest officers. The women received their training- in the 

 field. The inspection of woods, selection and survey of sample plots, 

 marking of thinnings, etc., were made by the officer in charge ; the 

 actual measurement of the trees and the working up of field data being 

 in the hands of the women assistants. 



For a detailed description of the methods used in measuring sample 

 plots, the reader should consult Bulletin No. 1 referred to above. A 

 sample plot comprises a small demarcated block of forest, the area of 

 which is accurately determined. The size of the majority of the sam- 

 ple plots ranged from 0.3 to 0.5 acre ; it was considered better to have 

 a large number of small plots than a few plots of, say, half an acre 

 and over. The plots were made as large as possible, but great diffi- 

 culty was experienced in finding pure, uniform, well-stocked areas of 

 any size. 



The trees of the main crop were numbered, girthed at breast-height 

 (4 feet 3 inches above the soil), and classified on paper according to 

 Hartig's method into five groups containing equal basal areas. The 

 mean sample tree was then calculated for each group, and two sample 

 trees in each group (i. e., ten trees in all) of mean girth at breast 

 height and typical form were selected- in the sample plot, felled, and 

 measured on the ground. From the volumes of these felled sample 

 trees the volume of the plot was calculated in the usual way. The area 

 of the sample plot being known, the corresponding figures per acre 

 were readily obtainable. 



In addition to these plots, a certain number of smaller areas, about 

 0.1 acre in size, were measured, chiefly in young woods. These have 

 been called sub-plots. They have been treated in the same way as the 

 plots, but the volume determination has been made usually from the 

 measurements of three sample trees selected as the mean of all the 

 trees in the sub-plot. 



The quarter-girth system^ of measurement has been used throughout 

 the survey. This system was adopted in preference to that employed 



^This is one-quarter of the circumference of the tree at 4 feet ?, inches above 

 the ground. To convert to inches of diameter muUiply the inclies quarter-girth 

 by 1.27. 



