OF ARTS AND SCIENCES. 



309 



As the deflection was constantly increasing, and was already more 

 than the deflection of Piece No. 7 when the load was first applied, it 

 seems to the writer that the beam would undoubtedly have in time 

 been broken by its load. 



The deflection of this beam is given in Table VI. 



TABLE VI. 



Deflections of Piece No. 8, Series No. 2, under 511 lbs. or § of its 

 Calculated Breaking Weight. 



The last piece in Series No. 2, Piece No. 9, was subjected to a load 

 of ^ of its breaking weight for 327 hours, during which time the 

 deflection constantly increased from 16.39 mm. (0.644 in.) to 19.07 mm. 

 (0.75 in.). The load was then removed and the "set" of the beam 

 measured. This set gradually decreased as the beam recovered itself, 

 until it was quite small, and probably the larger part of it was due to 

 the indentation of the beam at the points of support, something which 

 cannot well be prevented in a wooden beam. It will be seen from 

 table VII., that each time the load was applied the beam deflected a 

 little more than at the previous application of the load ; also that 

 the set increased much faster than the deflection. 



This tends to prove that the continued application and removal of 

 one half of the breaking weight of a beam will in a comparatively 

 short time cause it to break. 



