116 Mr. Bevan on the Strength of Timhei-, Sfc. 



regards the human eye, I have had very little opportunity for 

 investigation ; and though I have proved its existence, I can- 

 not say that it ever presented any distinctly coloured appear- 

 ance. This, however, will be accounted for when 1 come, in 

 another paper, to treat of the effects produced by this mem- 

 brane, on Vision, and to show the necessity that such a mem- 

 brane should exist. The name I propose to apply as most 

 descriptive of its appearance, is Membrana versicolor. 



XXV. On the Investigation of the Strength of Timber and 

 other Materials, with reference to the recent Experiments and 

 Comnnmications of Mr. Peter Barlow, Jun. By B. Bevan, 

 Esq. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



ALLOW me to express my thanks to Mr. Barlow for his 

 additional experiments, and for his candid reply to my 

 observations on his first paper. Experiments of this kind, 

 carefully conducted, are of considerable importance at this 

 time, and will for many years remain so, and tend to add a 

 lasting value to your Magazine. 



There are many persons who study the properties of tim- 

 ber and other materials, who have not the opportunity of 

 trying experiments on a proper scale ; and those who have the 

 means of doing so, frequently want the disposition, even if they 

 possessed the abilities. Communications of this nature are fre- 

 quently of more advantage to the practical mechanic than the 

 more abstruse and refined theoretical speculations, which al^ 

 ways confer great credit and value on your Magazine. Both 

 have their value ; but if we estimate their importance by the 

 number of persons likely to be benefited, those which come 

 within the reach of the practical man will be most valued. 



To encourage investigations of this nature, was the object 

 I had in view when I made my first remarks on Mr. Barlow's 

 communication, and not to excite any unpleasant feeling in 

 the author. My suggestion that it would be for the benefit of 

 science to observe as far as could be a uniformity in the specifi- 

 cation of the properties of timber and other materials, was not 

 intended to imply any censure upon him for adopting an arbi- 

 trary number, — which can readily be reduced to the modulus 

 of elasticity by any mathematician, — but to recommend the 

 use of that more generally adopted specification. 



As Mr. Barlow affirms he "does not see what advantage 



