14 



Now whether we adopt method a, (3 or y, we 

 may obtain the contents of the sample trees 

 either (1) by felling them and mfasuring 

 them accurately, or (2) by estimating their 

 contents standing. In either case, we may 

 seek to ascertain one of two things : (i) the 

 total solid contents of the trees, or (ii) sepa- 

 rately the quantity of each class of wood 

 or timber in them. 



h. By means of the r?c,^^-height. 



6, With the help of specially prepared tables of 

 volumes (volume-tables) or of form-factors. 



II. Valuation without any Mbasuukments {eye survey). 



A. Ocular estimate, after observation either (a) of the 



whole crop, or (S) of sample plots. 



a. Of the number of stems of different size-chisses. 

 6. Of volume of material (1) per acre, or (2) 

 standing in the whole forest. 



B. Kstimafe based on examination of figures given in 



existing yield-tables prepared either — 



a. Specially for the locality, or 



b. For the forest district or region. 



S. Choice hetween Complete Survey and Survey by Sample Plots. 



The valuation survey of a crop by means (if sample plots obvious- 

 ly requires very much less labour and time than a complete survey, 

 and must therefore be adopted whenever it is likely to fulKl the 

 objects of the survey. Its admissibility depends on three principal 

 considerations : — 



I. — The purposh! of thr shevby and the degree of accuracy 

 demanded. — The object of a survey is not necessarily alwa\s 

 to ascertain the total contents of the crop : we may desire , 

 to know only how much material on an average there is on 

 an acre, or we may seek to obtain figures required for the com- 

 pilation of certain tableSj or we may simply wish to determine 

 the quality of the soil or locality, and so on. In all these 

 latter cases the survey of well-selected plots, the area of which 

 has been accurately measured, is preferable to the survey of 



