the compression of the timber at the centre of support was diminished 

 to .77-in. 



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

 flection of .18-in. between the loads of 10,000 Ibs. and 30,000 Ibs.. is 

 1,01 1,450 Ibs. 



Table T shows the several readings. 



The weight of this beam on Nov. 3rd was 26.614 Ibs. per cubic foot. 



OLD SPRUCE. 



Beams LVII-LIX were three spruce stringers sent to the laboratory 

 by Mr. P. A. Peterson. 



Beams LVII and LVIII were cut at Galbraith's Mill, three miles 

 from Shcrbrookc, in 1886, and grew near the same place . They were 

 used in the construction of the bridge near Lennoxville in the winter of 

 1886-87, and had been in service until the summer of 1894, or for a 

 period of about eight years. 



Beam LIX was taken out of Bridge E 61 at Eoxton Falls during the 

 summer of 1894, and had Wn in service since 1885, i.e., for about eight 

 years. This stringer was purchased by Bridge-master MacFarlane, and 

 no further information has been obtained as to its history. The 

 stringer was boxed -in. at the ends on the bearings, and several sea- 

 son cracks were shown on the surface. 



Beam LVII was tested on the 21st April with the annular rings as 

 in Fig. 112. 



' - i 



jt-^ 



p 



ft*. L//+ 



The load upon the beam was gradually increased until it amounted 

 to 25,700 Ibs., when the beam failed by shearing longitudinally along 

 the surface of a season crack, the distance between the portions above 

 and below the plane of shear at the end being -in. 



Immediately after the fracture the jockey weight was run back until 

 the lever again floated, the load upon the beam being 21,000 Ibs. 

 This load was ihen gradually increased until it amounted to 24,700 Ibs., 

 when failure occurred by the tearing apart of the fibres on the tension 

 side and by a further crippling of the fibres on the compression side. 

 The lap at the end of the plane of shear was also increased to f-in. 



The maximum skin stress corresponding to the breaking load of 

 25,700 Ibs. is 3459 Ibs. per square inch. 



The maximum compression of the material at the support was .31- 

 in., so that taking the effective depth to be 14.69 ins., the maximum 

 compressive skin stress is 3526 Ibs. per square inch, the corresponding 

 tensile skin stress being 3b'78 Ibs. per square inch. 



If it is assumed that the usual iaw holds good for the whole of the 

 effective depth, then the maximum skin stress becomes 3607 Ibs. per 

 square inch. 



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

 deflection of .7-in. between the loads of 1500 and 12,500 Ibs., ia 

 1,123,400 Ibs. 



Table U shows the several readings. 



The weight of this beam on April 10th was 502 Ibs., or 33.82 Ibs. 

 per cubic foot ; its weight on April 21st, date of test, was 491 Ibs. 4 

 ozs., or 33.09 Ibs. per cubic foot, showing a loss of weight at the rate 

 of .0645 Ibs. per cubic foot per day. 



Beam LVIII was tested May 1st, 1894, with the annular rings as 

 in Fig. 113. Season cracks ran intermittently from end to end of 

 the beam. 34 



