TABLE 1. 
The data in Table 1 are derived from a considerably larger number 
of tests and are therefore somewhat more reliable than those of 
Table 2. Before an attempt is made to use these data, it is recom- 
mended that the entire text of this bulletin be read carefully, par- 
ticularly "Misuse of terms," page 6. Attention should be given to 
"Precautions to be observed in the use of data," page 4, to the 
explanation of the column heads, pages 7 to 18, and to the discussion 
and illustrations of the use of the variability figures given in Table 3. 
Where an apparent discrepancy is found between figures in this 
table and those in previous publications of the Forest Service, the 
data herein given may be considered as the most accurate (see p. 4) . 
Safe working stresses for the design of structural timbers should 
be based on the data in Table 1 rather than on those given in Table 2 
for reasons presented elsewhere in this bulletin, particularly under 
"Data on air-dry timber," page 7, and "Static bending," page 12. 
Safe working stresses will of necessity vary with the conditions 
under which the timber is used. Factors for obtaining working 
stresses for timber used in dry interior construction are given else- 
where in this bulletin as follows : 
Columns— Under "Maximum crushing strength," page 16. 
Details of joints — Under "Shearing strength parallel to grain," 
page 17, and under "Tension perpendicular to grain," page 18. 
26 
