STRENGTH AND TESTING OF TIMBER 
319 
of safety : — For timber in shearing, and compression across 
grain, 4 ; for columns under 15 diameters high and for end 
bearing, 5 ; for extreme fibre stress in transverse rupture, 
6 ; and in tension with and across the grain, 10. 
As there is such great variety in the results arrived at 
as to the strengths of timber tested by different people, only 
those tests which have been made upon a large number of 
samples of the same wood reduced to a standard degree of 
moisture have been given in this work, and the author has 
only gone so far into the question of testing timber as to 
show the inquirer what errors to avoid and lead him by 
references to more detailed information. 
Sufficiently accurate statistics are not yet available for 
dealing in great detail with tests on timber. 
