Stem Atialyses. icg 



history. An example of this method of tabulation is shown in 

 Professor Graves' well known book on "Forest Mensuration," 

 page 264, where the age of the tree at cross-section number i 

 (stump) was 60 years, and the last measured radius was conse- 

 quently recorded in column 6. The age of the second cross-cut 

 was 50 years, and the last measured radius was recorded in col- 

 umn 5, etc. When the volumes of the several sections are 

 computed for different decades there is a very large chance that 

 the wrong pairs of values for cross-sectional dimensions will be 

 selected, because, instead of being arranged one under the other 

 in the same column, the dimensions of the cross-cuts belonging 

 to any particular age of the tree are found in different columns, 

 and they must be selected by counting backward from the last 

 recorded measurement. This is one point at which the average 

 student has difficulty, and one which can be obviated entirely by 

 the use of a more logical method of tabulating the measurements. 

 A second point at which there is usually some difficulty is in the 

 doubling of the measurements given for radii, so as to obtain the 

 corresponding diameters. The form already referred to reads: 

 "Distance on average radius from heart to each loth ring — 

 inches" and the student not infrequently forgets to double the 

 value recorded for the radius, in order to obtain the diameter. 

 While this may seem like a trivial point, it is, nevertheless, one 

 which often leads to slight errors in doubling, or neglecting to 

 double at all; and when the use of a scale reading 2 : i would 

 obviate the necessity of recording radii, and permit the recording 

 of diameters directly, it seems wise to take simple precautions 

 and eliminate the chances of errors, by recording diameters in- 

 stead of radii. Stem analysis rules as now made by instrument- 

 makers, usually make readings of this kind easy by supplying two 

 scales', — one graduated to inches and tenths, for measuring di- 

 ameters, and the other for measuring radii graduated to half- 

 inches and twentieths, but reading as doubled inches and tenths, 

 so that radii may be read directly as diameters. The stem analysis 

 blank would therefore read, preferably, over the columns pro- 

 vided for the measurements: "Average diameter of section, by 

 decades," instead of "Distance on average radius from heart to 

 each loth ring." 



A third point, — and one which is a source of frequent errors 



