ozs-., or :!(>.>:: ll^. per ruble fiidt, ,-howing u loss (if weight l.clw. , g 

 "iivvr and the laboratory at the rate, o('.ll!'2 IK.. per culiic foot per 

 lav, and :i In-- n| wei.ji't wliili- in tlic l;i I i ira I. iry .11 I lie rate of 111 I' 1 

 i"T day. 



The time oconpied liy the tot wa^ l- 1 . min>. 

 OLD DOUULAS FlK. 



iteam- \\II \ \ V were eut to the l.ahoralnry liy Mr. P. A. 

 MO, Clue!' Kii-ineer cf the ( 'anad i an l':ieitic Kailway. 



The-e beam- were four old stringers taken IVoin trestle- numbered 

 188, 35, ::iii ami 789. 



Trestle H!* i- almut hail' my between Ci-eo Cantilc\er I'ridgt' and 

 !,vttoii. It wa- (i-ec ted in the early summer of 1884, anil the timbers 

 lia.l consequently been in position fur nine years. It is in a dry coun- 

 try. with very little rainfall, and subject to a hot sun in summer. The 

 stringer from this structure was cut out of a log probably grown on a 

 Mat. about three miles west of Hope, where most of the trees were wind- 

 hakeii. 



Trestle No. :\r> is about one mile west of Port Moody, and was built 

 in the early spring of 1.SS7, so that the stringer was in position for a 

 period of 6i years in a place subject to the heaviest rainfnll in the 

 province. The stringer was cut from a log most probably grown at 

 Point Urey, about eight miles from Vancouver. 



Trestle No. 31G is two miles cast of Spuzzum. The stringer from 

 rhis trestle was cut from a lug grown on a bench near Spuzznm about 

 500 feet above the sea-level. It was prepared and framed in 1881, 

 ind erected in 1882, so that it was eleven years in position in a district 

 with a climate similar t<i that of Nova Scotia. As the railway here 

 runs north and south, the sun had not the same effect upon the stringers 

 other parts of the line. 



Trestle No. 789 is ou Kamloops Lake, six miles east of Savona, and 

 was erected in the spring of 1885, so that the timbers had been in 

 -ervice for a period of eight years. The neighbourhood is dry, but the 

 trestle, being situated under a high bluff, is protected from the after- 

 noon sun. The stringer from this structure was cut out of a log prob- 

 ably growu about three miles west of Hope, at the same place as the 

 timbers used in structure No. 428. 



Beam XXII ftom Trestle 428, was tested Nov. 25th. 1893, with 

 he annular riii'.'S as in Fi<_'. 41. 



ft*" 



There wore two vertical 1-in. bolt holes in the timber, one near the 

 cntre and one at the end. There were also several season cracks in 

 the. timber, one being somewhat large. 



The load upon the beam, was gradually increased until it amounted 

 to 55,400 lb-.. when the beam failed by a longitudinal shear, as 

 in Figs. 4'2, i:;. 



The d'stance between the portions of the beam above and below the 

 plane of shear at the end was f ths of an inch. 



The maximum skin stress corresponding to the breaking load is 

 7086 Ibs. per square inch. 



The total compression of the timber at the centre was ,63-in., so that 

 'aking the effective depth at 15.0575 ins., the maximum skin compres- 

 sive stress is 7264 Ibs. per square inch, the corresponding tensile skin 

 'tress being 7898 Ibs. per square inch. 



15 



