504 TIMBER BONDS 



uniform periods of two or more years; and intermit- 

 tent when they are made at irregular intervals. Sus- 

 tained annual, periodic, or intermittent workings are 

 those under which the amount of wood cut is so regu- 

 lated that the productive capacity of the forest does 

 not decrease, but produces a sustained yield, which 

 likewise may be annual, periodic or intermittent. 



AVorking Area. The total forest area managed under a 

 working plan. 



AVorking Plan. A detailed and comprehensive scheme 

 for the best permanent use of the forest. 



AVorking Plan Renewal. The preparation of a new work- 

 ing plan for a given contract, when the present work- 

 ing plan has been carried out, or changed conditions 

 require its revision. 



Wrapper Chain. See Binding Chain. 



Yard. See Landing. 



Yarding Donkey. A donkey engine mounted upon a 

 heavy sled, used in yarding logs by drum and cable. 



Yield. The amount of wood at present upon, or which 

 after a given period will be upon, a given area. See 

 Present Yield; Future Yield; Accident Yield; Inter- 

 mediate Yield; Pinal Yield; Working. 



