Manchester Memoirs, Vol. li. (1907), No. 15. 



THE WILDE LECTURE. 



XV. The Structure of Metals. 



By J. A. Ewing, M.A., LL.D., F.R.S., 



Director of Naval Education to the Admiralty. 

 Delivered February 18th, igoj. 



I ought to apologise for bringing forward matter 

 which cannot possibly be new to an audience acquainted 

 with recent developments in various branches of 

 science ; but at least some part of the lecture may be 

 unfamiliar, and in order properly to lead up to that 

 I shall endeavour to state certain elementary facts 

 about the crystalline structure of metals, although these 

 are no doubt well known already by many of those now 

 present. Without such a statement it would be difficult 

 to show the relation between the facts as we have them 

 and the comparatively novel theory which I am going to 

 submit for your consideration. There is this further 

 excuse, that what I have to say deals with matter in which 

 I have had some little personal share in the way of 

 original investigation, dating now from a good many years 

 back. 



At the outset, then, it is important you should realise 

 that any metal, even the simplest and purest, is not by any 

 means a single homogeneous thing, but is a great aggre- 

 gate of distinct pieces which we call grains or granules. 

 Those of you who are familiar with the Alps may know 

 that if you examine the structure of a glacier, you find, 

 taking any great block of ice such as may fall from a 

 serac, that that block, when the sun plays upon it, 

 gradually becomes resolved into pieces somewhere about 



June 20th, 1907. 



