L891.] 



Young's Modulus for Crystals, fyc. 



387 



jpposite sides of the neutral axis, and one cannot be sure that the 

 rery slightly strained material of the central parts acts in the same 

 ray as that near the tipper and lower boundaries. 



In nearly all the substances experimented on, it was found that 

 rork was done in bending and unbending the beams, i.e., for a given 

 leflection the load was always less when the latter was being 

 liminished than when it was being increased. This effect was gene- 

 illy more apparent in metals than in hard crystals. 



On reference to the Table (p. 398), it will be seen that only ten of the 

 ion-metallic substances examined at all approach steel in stiffness. 



I regret that I have not hitherto been able to get a specimen of 

 liamond of suitable form for measurement ; but I hope to be able to 

 jive Young's modulus for this and some other crystals in a supple- 

 icntary table. 



