76 THE WOODSMAN'S HANDBOOK. 



instead of 4J feet. With small timber, that averages 6 to 10 

 inches in diameter, the error due to low measurements is" practi- 

 cally negligible, but with large timber it may seriously affect an 

 estimate. In old spruce, careless calipering has added 1 inch to 

 the diameters of 20 per cent of the trees. This means for every 

 1,000 trees an overestimate of 8,000 feet, or on an average on spruce 

 and hardwood lands about 300 feet per acre. Care also should be 

 exercised to place the calipers at right angles to the axis of the tree. 

 It is obvious that a considerable error may result if the calipers 

 are placed obliquely on the trunk. When there is a bulge or other 

 normal swelling at breastheight, the measurement should i>e taken 

 just above and not below the obstructions. In tropical countries, 

 or with certain trees, like cypress, where many of the trees are but- 

 tressed, the measurement can not be taken at breastheight, and 

 special methods of grouping are used. 



In an estimate of merchantable timber only apparently sound 

 marketable trees are included, and frequent errors in estimating 

 come from counting unsound trees. Inexperienced or careless men 

 will measure trees which may appear sound and merchantable, 

 but which are really defective. Great care must be exercised to 

 scrutinize each tree for signs of defect. Usually decay manifests 

 itself by some external sign, such as punk knots, white resin, un- 

 healthy crown, broken top, or dead limbs. A cruiser must know 

 these signs. If he is working in a new country, he should associate 

 with him some local woodsman who is familiar with the character 

 of the timber. 



In a great deal of government work trees below the merchantable 

 size and sound trees of species not yet merchantable are measured 

 in connection with preparation of working plans. 



The methods of determining the volume of the trees on the strip 

 surveys are described in later sections. 



RECORDING THE MEASUREMENTS. 



The diameter measurements ar^ recorded in a tally-sheet note- 

 book. The tally sheet is ruled in columns; the first column shows 

 the diameter classes, by inches or by groups of 2 or more inches,* 

 and the other columns are for the various species. A special form 

 of tally sheet used by the Forest Service is bound in books which 



