432 



March 26, 1857. 



Major-General SABINE, R.A., Treas. and V.P.,, in the Chair. 

 The following communications were read : 



I. " On an Element of Strength in Beams subjected to Trans- 

 verse Strain, named by the author 'The Resistance of 

 Flexure/" (Second Communication.) By WILLIAM HENRY 

 BARLOW, Esq., F.R.S. Received March 12, 1857. 



(Abstract.) 



In his former paper on this subject the author pointed out the 

 existence of an element of strength in beams when subjected to trans- 

 verse strain, the resistance of flexure which had been omitted in 

 ihe generally received theory ; and the object of the present experi- 

 mental inquiry is to elucidate more clearly the general bearing of 

 the subject, and determine more precisely the laws which govern 

 this resistance. 



The forms of beam employed in the experiments formerly de- 

 scribed were only of two kinds solid rectangular bars and open 

 girders ; in the present experiments other forms have been used, 

 namely, square bars broken on their sides, square bars broken on 

 their angles, round bars, beams of the I section broken with the 

 flanges horizontal, and similar beams broken with the flanges ver- 

 tical M. 



The results of these experiments are exhibited in Tables, together 

 with those of the former series ; and the author employs them, in 

 the first place, to test the accuracy of the existing theory, by com- 

 paring the resistance of the outer fibres or particles of each of the 

 forms of beam, calculated on that theory, with the actual tensile 

 strength of the metal as obtained by direct experiment. From this 

 comparison applied to the different forms of beam, it would follow 

 that the resistance at the outer fibre varies from 25,2/1 Ibs. to 

 53,966 Ibs., while the tensile strength of the metal, obtained by ex- 

 periments on direct tension, averages onlv 18,750 Ibs. ; and the dis- 



