12 



Mr. W. N. Bond on the Properties of 



This fio-. !2 shows for comparison the forms of the 

 following specimens when subjected to a central load: (a) the 

 elastic curves (theoretical), (b) the curved forms of some 

 bent crystals, (c) the curve of a celluloid strip, and (d) some 

 curves obtained with strips of lead. 



Fiar. 12. 



It will be seen that the celluloid is more curved at the 

 central parts than the corresponding elastic curves. This is 

 due, partly at least, to there being a plastic bend of the 

 celluloid at the central portion (as was noticed on removing 

 the load). In the case of the lead, two of the curves shown 

 have almost equal depression. Of these, the one with the 

 sharper bend was bent more rapidly than the less pointed 

 one (i.e. a larger load was applied). The specimens were 

 made from the same sheet and of the same dimensions. In 

 the case of more rapid bending where the stress was every- 

 where greater than in the slower case, the bending is more 

 pronounced where the bending moment is greatest. Thus 

 the rate of bending increases more rapidly than in direct 

 proportion to the stress. This is in agreement with the results 

 obtained by Andrade*. If we do not consider his initial 



* Andrade, " On the Viscous flow of Metals," Proc. R. Soc. A, ^ ol. 

 lxxxiv. 1910 ; & vol. xc. 1914. 



