OF ARTS AND SCIENCES. 307 



Series No. 2. 



In commencing this series of experiments five of the beams were 

 subjected to loads of 30 and 40 lbs., and the deflection measured 

 at the end of one hour from the time the load was applied. From 

 these deflections the moduli of elasticity have been calculated. The 

 values given in Table II. are the average of the values obtained from 

 the deflection under 30 lbs. and the deflection under 40 lbs. 



Having determined the moduli of elasticity of these pieces, five 

 pieces of the series were broken by means of a gradually increasing 

 load, and from their breaking load the modulus of rupture of each 

 piece was computed. The average value of these five pieces (Nos. 

 1-5) was then considered to be the average value for the whole series, 

 and the breaking weight of the remaining pieces of the series was 

 computed on this basis. 



Before attempting to break the remaining pieces, a load of 50 lbs., 

 about -j^ of its breaking load, was applied to piece No. 6, with the 

 object of determining if the deflection under this slight load would 

 continually increase. The load was kept on the beam 288 hours, and 

 the deflections, taken at intervals, are given in Table IV. From these 

 it will be seen that the deflection increased very rapidly for the first 

 24 hours, and then quite regularly, but slowly, for 192 hours, and 

 that after that it continued to decrease for 72 hours, when it slightly 

 increased again. 



As it was desired to use the machine for the more direct purposes 

 of the experiments, the piece was removed from the machine, but it 

 would have been interesting to have watched the further action of the 

 load on the beam. 



During the time that the deflections decreased, the weather was very 

 wet, and it is the opinion of the writer that the deflections were some- 

 what affected by the change in the condition of the atmosphere. It 

 should be observed that the greatest increase of deflection was very 

 small, being only 0.44 of a millimetre, or about 0.017 of an inch. 



After allowing this same beam several days in which to recover 

 from the strain caused by the load of 50 lbs., 574 lbs., or f of its cal- 

 culated breaking load, was suspended from the beam, and the deflection 

 measured at frequent intervals, with the results shown iu Table IV. 

 After carrying the load 260 hours the beam broke. 



