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V, Eflects of Strain on the Crystalline Structure of Lead. 
By J. C. W. Humfrey, B.Sc., Viet., 1851 Exhibition Research Scholar [University 
College, Liverpool), St. Johns College, Cambridge. 
Commnnicated by Professor Ewing, F.R.S. 
Received May 28,—Read June 5, 1902. 
[Plates 2-6.] 
The effects of strain upon the crystalline structure of metals and tlie subsec[iient 
effects of annealing at low temperatures have already been studied by Ewing and 
liosENHAiN,"^ and the work described in the following pages is in many ways a 
continuation of theirs. A variety of lead was obtained in which the crystalline 
structure was on a particularly large scale. This furnished a metal specially well 
adapted for experiments on the influence of strain on crystalline structure, and the 
author, on the suggestion of Professor Ewing, was successful in obtaining single 
crystals of sufficient size to furnish a test piece possessing a uniform orientation 
throughout the part under test. As the effects of a strain could then he studied in 
individual crystals, the problem was greatly simplified. 
The material used was a pure lead, commercially known as “ chemical lead,” its 
chief use being for purposes such as the lining of acid chambers. It is obtained by 
treating ordinary furnace lead in Pattinson crystallisation pots, and by this process 
practically all other metals which were originally alloyed with it are removed. Tlie 
first sample obtained had been cut from a casting, and was about G inches by 4 inches 
in area by 1|- inches deep. One of the large faces had been in contact with the air 
during solidification and the other with the bottom of the mould. The former 
showed in a very beautiful manner, and without any treatment, the crystalline 
structure of the material. The crystalline grains were clearly lined out by the slight 
differences of level at which they had formed, the boundaries showing up as fine 
lines. These grains varied from about sep inch to 4 sq. inches in area and were of 
quite irregular shape. Alany of them exhibited distinctive markings on tlieir 
surfaces, these generally taking the form of slight lidges. In many cases one fairly 
* ‘Phil. Trans.,’ A, vol. 193, 1899, pp. 353-377, and ‘Phil. Trams.,’ xV, vol. 195, 1900, pp. 279-301. 
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