319 



March 29, 1855. 

 THOMAS BELL, Esq., V.P., in the Chair. 



The following communications were read : 



I. " On the existence of an element of Strength in beams sub- 

 jected to Transverse Strain, arising from the Lateral Action 

 of the fibres or particles on each other, and named by the 

 author the ' Resistance to Flexure/ " By WILLIAM HENRY 

 BARLOW, Esq., C.E., F.R.S. Derby. Received February 23, 

 1855. 



The author commences by observing, that under the existing 

 theory of beams, which recognizes only two elements of resistance, 

 namely tension and compression, the strength of a beam of cast 

 iron cannot be reconciled with the results of experiments on the 

 direct tensile strength, if the neutral axis is in the centre of the 

 beam. 



He then proceeds to describe experiments made on two solid 

 beams of cast iron to determine the position of the neutral axis. 

 The beams employed were 7 feet long, 6 inches deep and 2 inches 

 thick, on each of which small vertical ribs were cast, 12 inches 

 apart ; nine small holes were drilled opposite to each other in each 

 rib, for the purpose of inserting the pins of a delicate measuring in- 

 strument. The distances of the holes of the centre division of both 

 beams were measured under various strains, and the results show 

 that the extensions and compressions proceed in an arithmetical 

 ratio from the centre to the upper and lower sides of the beam ; and 

 that at any given distance on either side of the centre, the amount 

 of extension is equal to the amount of compression. 



The position of the neutral axis being thus conclusively ascertained 

 to be in the centre, it is shown that, not only the ultimate strength, 



VOL. VII. 2 K 



