230 



On the strength of Pine and Spruce Timber 



the load was immediately removed from the platform, a new speci- 

 men substituted, the index readjusted to the zero of the scale, and 

 the same operations repeated. By this method the number of useful 

 observations during each trial, was greatly augmented without causing 



any additional trouble. 



From the foregoing description, it will be seen that die loads were 

 not allowed much time to act upon the beams, from which it follows 

 that the weights producing the different deflexions are rather over- 

 rated. With regard to the object for which these trials were insti- 

 tuted, this was a matter of no importance, as it could not affect the 

 relation between the different kinds of wood, and upon making some 

 experiments to ascertain the amount of error, it was found so- srnal 

 th;it it might with safety be neglected. 



* A * * « ill -*-^ 



In tin: first trial, 



[A 



load of 26<U pounds, which produced a deflexion of f yh ot an incn 



to a foot, instead of being immediately removed, was allowed to rc- 



uain suspended for two hours and forty minutes, when it was iounc 



■ i . • i ■» * a t I /\ /m* -- (' .,\nh 



of an inch. 



that the center of the beam had sunk only 0.0. 



The foregoing observations, with a few explanatory remarks, win, 

 it is hoped, render the following tables intelligible. 



Table (A.) Detailed Statement of Experiments to determine the rehiUrr stijf- 



ness of White Pine, Sjiruce and Southern Pine, 



a 



.2 



0> 



White Pine. Spruce. 





c 

 ~ 



4) 



* i 



C -i 



e 



c « 





f* * 



■j 



y. 



a 



- o 



£ 



• 





« ■ ~ § § 



iithcrn Pine- 





U 





, 0.0*22 

 0.177 



0.355 



0.532 

 ).710 



J.G2 . 



0.177 



0.355 



1 



a. 



.- 



.. 



J 



A 0.532!; •' 2074 



~> 



.. 





Ill 



836 

 1516 



21 5 



26< 52 



126 



715 

 114* 



O 



r£ C 



J* 





4 



44 



it 







_4 

 4 



0.7 iO I 



- I 



ii 



271 18 



1 24 i 



737 

 ! * 55 



1960 

 2683 



1 3 1 



97 3 



] 729 



"2464 



"i3li9 





c — 



'5 ~" 



Whole 



REMARKS. 



th of 



specimens m feet 9-380 



■^ * \ * 1 -i. ■ i > 



Bearing length in 



ac 



feet 



i 



.1 



7 



44 

 tt 



).02„ ([ ., 

 1 0.17* '■-' 



■t ii 



i 



4 2 - 0.355 « 

 " 0.532 

 0.710 



_3 



40 



_4 

 4 



1 2» '» 

 7M 



1491 

 2125 



2733 



ti 



4fc 

 it 

 tfc 

 (4 



I4< 



968 



1816 



2449 



3098 



M 



44 



217 

 1187 



2252 



32( >(> 



S < )78 



5.5 



Breadth in inches 2.7- 1 

 Depth in inches 



In these trials, each 

 specimen, upon being re- 

 lieved of the load pro- 

 ducing the greatest de- 

 le h\ 





9 



44 

 44 



217 



1 1 45 



V. 



3037 



3996 



flexion, sprung bac 

 die elasticity of the wood 

 until the center came 

 within about 0.046 inch- 

 es of being as high as it 



was before the experi- 

 ment commenced. U ] 1S 

 deflexion of 0.04G inch- 



5, would have been still 

 further reduced had more 

 time been allowed. 



