catch the plummet line and keep it in place until the figure indi- 

 cated has been read. 



For measuring lengths, graduated rules or tapes may be used. 

 Where great accuracy is required, the length of a felled tree or log 

 should be measured along, or parallel to, its axis, and not on its 

 slopping surface. 



The sectional area of a log or tree can very rarely indeed be 

 obtained directly. In nearly every case the girth or diameter must 

 be measured, and the area of the section determined as if the sec- 

 tion were a circle. Area = -isU — L = 1L (diameter)* or according 



to trade custom =1 \ 



Girths are measured with tapes. It is convenient to have tapes 

 graduated on both sides — one side for reading the girtb, and the 

 other for reading the corresponding diameter. The zero end of 

 the tape should be furnished with a sharp metal point that can be 

 easily fixed in the bark of tlie tree, so that one person may be able 

 to measure any stem, no matter how thick it is. As a circle en- 

 closes a greater area than any other plane figure of equal perime- 

 ter, and as the sectional outline of trees is seldom quite circular, 

 the contents of a log or tree calculated directly from its girth by 



the formula i^ '— will usually be in excess of the true contents. 



Unless the contour of the log is circular, it is impossible to obtain 

 by girth measurement the circumference of the circle which encloses 

 the same space as the section whose area is required. Irregularities 

 of outline, due to fluting, bark, etc., cannot be overcome in measure- 

 ments of girth, whereas, as we shall presently see, they can more or 

 less successfully be allowed for in measuring diameters* Experi- 

 ments made in Baden prove that girth measurement yields a result 

 that is from six to ten per cent, greater than that obtained by means 

 of diameter measurement. It is, however, obvious that in cubing 

 logs departing from the cylindrical form, the measurement of the 

 girth is more to be relied on than the measurement of a single 

 diameter. 



When the true contents of a log are to be deduced from diame* 

 ter measurement, that diameter should be sought which, considered 

 as the diameter of a circle, gives a result as nearly as practicable 



