116 Mr. T. Andrews. [June 5, 



transversely to the line of the cold crystallising force, and from my 

 former experiments in this direction (' Roy. Soc. Proc.,' vol. 40, 1886, 

 p. 544), I think there appear substantial indications that ice may 

 expand nnequally in different directions. Messrs. McConnel and 

 Kidd have shown, in their experiments with glacier ice, that 

 "ordinary ice, consisting of an irregular aggregation of crystals, 

 exhibits plasticity, both under pressure and under tension at tem- 

 peratures far below the freezing point, down to 9 at least, and 

 probably much lower." The experiments recorded on Diagram I 

 now practically demonstrate the latter supposition, and I found the 

 plasticity at the lower temperature to be very considerably reduced. 

 Mr. J. Y. Buchanan, F.R.S., in his paper on "Ice and Brine" 

 (' Edinburgh Roy. Soc. Proc.,' vol. 14, 1888, p. 129), has expressed 

 notions of the plasticity and flow of glacier ice which tend to confirm 

 the views of Messrs. McConnel and Kidd on this subject. In this 

 direction the experiments on pure ice, Diagram I, compared with 

 those on pond ice, Diagram II, have shown that ice frozen from 

 water containing saline constituents is more plastic than the ice 

 frozen from pure distilled water. 



I hope that the experiments of this memoir may help to afford 

 information in connexion with the interesting subject of the plasticity 

 of ice. 



Appendix. 



Attention has very recently been drawn to the manner in which 

 lake ice has a tendency to crystallise, in a series of interesting 

 letters published in ' Nature,' 1889, by Mr. Thomas H. Holland, 

 Mr. T. W. Backhouse, Mr. T. 1). Latouche, Messrs McConnel and 

 Kidd, and others. I have myself also frequently noticed the six- 

 rayed starlike figures and skeleton triangular forms on natural pond 

 ice, and other similar indications of the tendency of lake ice to the 

 hexagonal form of crystallisation. 



III. " The Passive State of Iron and Steel." Part I. By 

 THOS. ANDREWS, F.R.SS.L. and E., M.Inst.C.E. Received 

 May 18, 1890. 



The singular metallurgical phenomenon of the passive state of iron 

 presents many features of interest, affording a wide field for original 

 research. The knowledge we possess on this peculiar and obscure 

 subject is not, however, very extensive, owing possibly to the difficul- 

 ties encountered in devising suitable methods of research in relation 

 thereto. The author, therefore, approached the investigation with 

 considerable diffidence, feeling greatly the difficulties accompanying 



