278 On the Transverse Strain, 
The direct strength of a square inch of fir, 
according to Muschenbroek, is 8330 pounds, 
which above is denominated s ; and the depth 
of the surface of tension being to that of 
compression as 23 to 25 (art. 32): In order 
to find the neutral line we have, 23 +25: 
23 :: 12 (the depth) : BTS inches=a, 
the depth of tension. ..g = "at ;p= S x 5°75, 
and p’= + (12—5:75), by the properties of the 
centres of gravity and percussion. .*. p 4+ p/= 
2 : 
3 X 12(the wholedepth) = 8 inches. Hence 
the formula forthe strength a becomes 
8330% KX 5°75 X3BX8 
5:7 
2 
575108 = 5322 pounds nearly. 
Example 2d. What weight must be sus- 
pended from the middle of a beam of Quebec 
oak to cause a tension in its lowest fibres of 
8000 pounds to the inch, the beam being 
20 feet long and one foot square, and sup- 
ported ona wall at each end ? 
Here s is 8000 ; and since half the weight 
is supported by each wall, it is evident that, 
if we suppose the beam fixt firmly at its mid- 
dle, and then seek for the resistance at one 
end necessary to produce the given tension 
on its side, the double of that would be the 
