On the Plasticity of an Ice Ciystal. 323 



Rowland (H. A.) and C. T. Hutchinson. On the Electromagnetic 

 Effect of Convection Currents. 8vo. [London] 1889. 



The Authors. 



Butley (F.) On Composite Sphernlites in Obsidian, from Hot 

 Springs near Little Lake, California. 8vo. [London] 1890. 



The Author. 



Sang (E.) Exhibition of Curves produced by the Vibration of 

 Straight Wires. 8vo. [London] 1889. The Author. 



Slater (J. S.) Description of an Improved Armillary Sphere. 8vo. 

 [London'] 1890. The Author, 



.ckermann (A.) Index to the Literature of Thermodynamics. 8vo. 

 Washington 1890. The Author. 



March 12, 1891, 

 Sir WILLIAM THOMSON, D.C.L., LL.D., President, in the Chair. 



The Right Hon. Lord Hannen, whose certificate had been sus- 

 pended as required by the Statutes, was balloted far and elected a 

 Fellow of the Society. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



Kie following Papers were read : 

 On the Plasticity of an Ice Crystal." By tlie late J. C. 

 McOoNNEL, M.A. Communicated by R. T, GLAZEBROOK, 

 : F.R.S. Received January 24, 1891. 



Two years ago, in the ' Proceedings of the Royal Society,' was pub- 



ished an account of some experiments on t"he plasticity of ice made 



>y Mr. Kidd and myself. We proved the oft-repeated statement, that 



lacier ice is not plastic under tension, to be erroneous, and showed 



bat any ordinary bar of ice composed of several crystals will yield 



ontinuously either to pressure or tension. But we found that a bar 



at out of a single crystal with its length at right angles to the optic 



sis showed no signs of continuous stretching even under half the 



peaking tension, and other experiments convinced us that an ice 



ystal will not change its shape under either tension or pressure 



^plied at right angles to its optic axis. These results seemed to 



;nder it highly probable that an ice crystal was not in any way 



astic, and though after the winter was over we wished we had varied 



ir experiments more, yet we quite expected that further investiga- 



