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VIII. The Crystalline Structure of Metals. (Second Paper.) 
By J. A. Ewing, F.R.S., Professor of Mechanism and Applied Mechanics in the 
University of Cambridge , and Walter Rosenhain, B.A., St. Johns College , 
Cambridge , 1851 Exhibition Research Scholar , University of Melbourne. 
Received July 12, 1900—Read, in Abstract, May 31, 1900. 
[Plates 3—13.] 
The investigations described in the present paper deal principally with the 
phenomena of annealing. They form a continuation of the research described in the 
Bakerian Lecture for 1899 (‘Phil. Trans.,’A, vol. 193, 1900, pp. 353-377). In iron, 
steel, and brass these phenomena have been studied with the aid of the microscope 
by various workers, among whom Arnold, Charpy, Stead, and Roberts-Austen 
should be particularly mentioned. As a result of their labours it is well known that 
annealing is accompanied by a re-arrangement of the crystalline grains of the metal. 
Thus, when a piece of iron is strained in tension its crystalline grains become 
elongated in the direction of tension ; but when the specimen has been subsequently 
annealed by being heated to a bright red, all signs of such elongation disappear from 
the crystalline pattern revealed by the microscope. In fact it is not generally 
possible to find any definite connection between the crystalline pattern seen in the 
same specimen before and after annealing. In general, the pattern seen after 
annealing resembles that found in a similar specimen before it has been strained, 
but the scale and character of the pattern produced depend very much on the 
details of the annealing process, particularly upon the temperature applied, the time 
of its application, and the rate of cooling. Arnold and Stead have shown that 
prolonged annealing tends to produce large crystals in iron and steel. But even 
short exposure to a suitable temperature is well known to produce complete re¬ 
crystallisation, and it has been suggested that these changes occur at critical points 
corresponding to the “ arrest-points ” in the cooling of the metal. These arrest- 
points indicate evolutions of heat, and it is natural to suppose that they are evi¬ 
dences of re-arrangement of the structure of the metal. 
At the outset of the present research we hoped to observe this change taking place 
under the microscope. Although the experimental difficulties of keeping a specimen 
under microscopic observation while it was being heated were successfully overcome, 
the attempt to watch the re-crystallisation of iron failed. 
10.12.1900. 
