314 
TIMBER 
for testing, probably not so much. One hundred tests on 
" yellow pine " (pitch pine) beams 3 inches by 10 inches to 
about 4^ inches by 12| inches, and one piece 6 inches by 
16^ inches, made by Lanza, gave an average modulus of 
rupture of 7,442 lbs. ; yet he says " I should not feel justified 
in using a greater number than 6,000 lbs. per square inch," 
although only nine of the samples tested fell below that 
limit.^ Laslett, on the basis of small pieces of the same 
timber, gave the minimum modulus of rupture as 10,044 lbs. 
per square inch, Hatfield as 9,000 lbs. per square inch, and 
Eodman 8,796 lbs. per square inch, proving what we have 
said about the mistake of trusting the results of tests made 
on small and perfect samples of timber. 
Again, for spruce beams tested by Lanza the average 
modulus of rupture in 161 tests on pieces from 2 inches by 
7 inches to 7 inches by 12 inches was 4,521 lbs. per square 
inch, yet he says that although only seven of the tests fell 
below 3,000 lbs., that is all that could with safety be used, 
though if timber were specially selected he might allow 
4,000 lbs. For similar timber Eankine gives 9,900, Hatfield 
7,506, Laslett 7,506, and Trautwine recommends 5,400 lbs. 
per square inch. 
Mr. H. D. Smith, M.LC.E., tested to destruction a number 
of Quebec yellow pine beams, 9 inches by 9 inches, 18 inches 
by 9 inches, and 12 inches by 12 inches, with a span of 14 ft., 
and the mean transverse strength was found to be 3,807 lbs. 
per square inch. On beams of the same timber, tested under 
similar conditions and at the same place in 1875 by Mr. 
C. Graham Smith, the mean transverse strength was 4,491 lbs. 
per square inch for a scantling of 14 inches by 15 inches, 
with a clear span of 10 ft. 6 inches.^ For this same class of 
^ " Ai)plied Mechanics," G. Lanz.i, 1899. 
2 Mill, of Proc. Inst. C.E., Vol. CXXMIL, und EmjiiieerirKj, 
May 7tli, 1875. 
