FOREST MENSURATION. 189 



For Measuring Land Acres the ordinary steel tape, grad- 

 uated on one side in feet, tenths, and hundredths, and on 

 the other side in Unks for convenience in computing acre- 

 age, is used, the 100-foot length being preferred. For the 

 same purpose a steel chain is also used, and with the chain 

 or tape should be a set of marking-pins and ranging-poles. 

 In laying out small rectangular areas, as a sample acre, 

 a cross-staff head, an angle mirror, or an angle prism is 

 used, but for more extended surveys and for road and ditch 

 work a transit and level would be advisable, while for the 

 location of lost corners the magnetic compass might have 

 to be resorted to. 



For the Rough Land Measurement of a Valuation 

 Survey a Steel Chain Thirty-three Feet Long is used. 

 This short chain is attached to a stout leather belt about 

 the waist of the tallyman, whose hands are then free 

 to carry the tally board holding notebook or tally blanks, 

 and to work with a lead-pencil. A small magnetic com- 

 pass by which the tallyman directs his course is fixed 

 on one corner of the tally board. 



The Diameters of Trees and Logs are taken with a pair 

 of wooden calipers of convenient size for the timber of the 

 district. A limb or scale bar, graduated in inches ar.d 

 tenths, has a fixed arm standing out at right angles at 

 one end, while a second arm is movable along the bar 

 so that the trunk of a tree may be enclosed between them 

 and the diameter read directly from the scale. The 

 fixed arm is held in place by a screw so that it may be re- 

 moved for packing and transportation, or so that a broken 

 part may be replaced. The other arm has an adjustable 

 plate which keeps it at right angles to the scale bar when 

 pressed against the tree. Sometimes the circumference 

 of the tree is measured with a steel tape, one side of which 

 is graduated to give diameters of circles whose circum- 

 ferences are read from the other side. 



