118 PRELIMINARY MATTERS. 



4. Conversion of an Intermittent into an Annual Rottal. 



A rental li is due after n years, and again every n years for 

 ever ; it is equal to an annual rental of — 



^ - X -O;) . . . (XL) 



1-0/' 



A rental 11 is due after m years, and then every n years for 

 ever; its value is equal to an annual rental of — 



'■ = %^'x-o. . .,xii.) 



A rental II is due now, and again every n years for ever ; 

 its value is equal to an annual rental of — 



All the above calculations can be made with logarithms, 

 or by means of tables, ^Yhich give future or present values 

 for various rates of interest. The tables in Appendix II., 

 page 340, which give the vahies for Formula I., II., YIIL, 

 and YL, suffice for all ordinary forest calculations ; they will 

 be utilised in the subsequent chapters. 



Section IV. — Estimate of Eeceipts and Expenses. 

 1. Ilcceipts. 



The receipts of forests are derived from a variety of pro- 

 duce, which are generally divided into two classes : Major, or 

 principal, produce and minor produce. 



(I. J/ ajar J'rodiirc. 



This comprises all yields of wood, that is to say, timber and 

 firewood. Bark is generally included; if it is severed from 

 the timber before disposal, it is sometimes classed as minor 

 produce. 



