Tlie load upon the beam was gradually increased until it amounted 

 t> 13,800 Ibs., when the beam failed by the crippling of tlie 

 fibres on the compression face, Figs. 54, 55. The load was still further 

 increased until complete fracture took pbce by the tearing apart of 

 the fibres on the tension faco under a load of 17,170 Ibs. The (-rippling 

 was in line with a knot running through tlie timber from back to 

 front, :is in the Figure. 



The maximum skin stress co-responding to the load of 13,800 Ibs. is 

 3937 Ibs. per square inch. 



Tlie total compression of the timber at the centre was .2-in., so that, 

 taking the effective depth as 13.05, the maximum skin comptessivo 

 stress would be 3994 Ibs. per sq. in., the corresponding skin tensile 

 stress being 4119 Ibs. per square inch. 



Assuming the ordinary law to hold good for the whole of the effective 

 depth, the maximum skin stress would be 4059 Ibs. per square inch. 



The co-efficient of elasticity, as determined by an increment in the 

 deflection of ,885-in. between the loads 1,000 and 8,000 Ibs., is 

 1,235,000 Ibs., and as determined by an increment in the deflection of 

 .5-in. between the loads 2,000 and 6,000 Ibs.. is 1,248,990 Ibs. 



Table K shows the several readings. 



The weight of this beam, on March 10th, was 392 Ibs. 2 ozs., or 

 37.56 Ibs. per cubic foot, and on March 13th it was 379 Ibs. 4 ozs., 

 or 36.3!) Ibs. per cubic foot, showing a loss of weight in the laboratory 

 at tlie rate of .39-lb. per cubic font per day. 



Beam XXVII was tested April 5th, 1894, with the annular rings 

 as in Fig. 56. The beam was cut from the heart of the tree, and the 

 darkened portion in the Figure, was sapwood. 



56 



rgn 



front o~</\6ac.A wirnt ofetftfhf \off*ff*-li~ 



fig 57. ffg-S'Q. 



The load upon the b^ani, was gradually iucreased until it amounted 

 to 17, 700 Ibs., when ths beam failed by the tearing apart of the fibres 

 on the teni-iidi fice, Figs. 57, 58, at a resin pocket, the fracture 

 showing a fine resinous surf.uv. 



The minimum skin stress corresponding to the breaking load is 

 5219 Ibs. per square inch. 



The total compression of tlie timber at the centre was .34-in., so that 

 taking 12.785 ins. as the effective depth, the maximum skin compres- 

 sivc stress wuuld be 5 HI Ibs. per square inch, the corresponding skin 

 tensile stress being 5707 lb~. pjr square inch. 



Assuming the ordinary law to hold good for the whole of the effec- 

 tive depth, the maximum skin stress would be 5501 Ibs. per square 

 inch. 



The co-effic cnt of elasticity, as deduced from an increment in the 

 deflection of 7-in. between the loads 1500 Ibs. and 7500 Ibs., is 1,418,500 

 Ibs. 



Table K gives the several readings. 



The total weight of the beam on March 10th was 46 Ibs. 12 ozs., or 

 41.51 Ibs. per cubic foot ; the total weight on April 5th, the date of test, 

 wa-. 397 Ibs. 4 ozs., or 36.50 Ibs. per cubic foot, showing a loss of 

 weight while in the laboratory, ;it the rate of ,192-lbs. per cubic foot 

 per day. 



Beam XX VIII. This beam was cut from the heart of the tree, and 

 was tested April 20th, 1891, with the annular rings as shown in Fig 

 59. 



20 



