THE 



PHILOSOPHICAL MAGAZINE 



AND 



ANNALS OF PHILOSOPHY. 



[NEW SERIES.] 



APRIL 1832. 



XXXII. Observations on Mr. Barlow's Expei-iments on the 

 Strength of different Kinds of Wood. By B. Be van, Esq. 



To the Editors of the Philosophical Magazine and Annals. 

 Gentlemen, 

 T HAVE perused the valuable communication of Mr. Bai*- 

 -*- low in your last Number, on the strength and elasticity of 

 several species of wood ; and join in regret with Mr. Barlow, 

 that the experiments on Acacia were not more complete. 



Some time since, an opinion was held by some carpenters in 

 Northamptonshire, in favour of the superior strength and dura- 

 bility of Acacia, and a prime specimen was sent to me for trial. 

 I found it inferior to good oak in strength, and something in- 

 ferior in elasticity; but as to durability, I am not aware of any 

 proper test ; but from the texture and appearance on fracture, 

 I should esteem it very inferior. 



From my experiments on that species of wood, I can supply 

 the omission in the fourth column of Mr. Barlow's table. 

 The modulus of elasticity of Acacia by my experiments being 

 4,560,000 feet, from which it will be easy to deduce the de- 

 flection of any scantling under a given pressure, and for the 

 particular case of Mr. Barlow, whence ^ = 50 b = d = 2 



,. , 1 T •. ^rm 1, 710X4,560,000 



and 8=1, and specinc gravity 710, we have rv^rz 



' ° •' 4500 



= 720 nearly for the weight required to produce a deflection 



of one inch. 



It will be observed by persons accustomed to experiments 

 of this nature, that the deflection of one inch approaches too 

 near the ultimate flexure to give a fair measure of the elastic 

 force of the specimen; the average oI'Mr. Ijiu'low's experiments 



N.S. Vol. 11. No. 6 k April 1S32. 2 I being 



