The effects of strain upon the crystalline structure of metals and the subsequent effects of annealing at low temperatures have already been studied by Ewing and Rosenhain, 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 be 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. The first sample obtained had been cut from a casting, and was about 6 inches by 4 inches in area by 1½ 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 ½sq. inch to 4 sq. inches in area and were of quite irregular shape. Many of them exhibited distinctive markings on their surfaces, these generally taking the form of slight ridges. In many cases one fairly large ridge ran down the centre of the crystal, and from this others branched away at right angles, giving the appearance of a sort of skeleton.