-4:2 
PEOFESSOR J. A. EWIXG AXD MR. J. C. AV. HIAAIFREY OX THE 
our purpose of possessing a clearly defined and fairly large crystalline structure, yell 
adapted yhen polished and etched to exhibit the characteristic lines knoyn as “ slip- 
linesor “ sh 2 )-hands,” yhich ajDpear in ordinary testing when any portion of the 
material has passed its limit of elasticity under strain.* We used the metal in the 
form of rods with a rectangular section, the dimensions being aj^proximately 0‘3 inch 
by OH inch, and to make the structure as uniform as possible these were in all cases 
annealed by being kejit for about two hours at a duU red heat, while enclosed in a 
tube filled yfith lime, in a jnufile furnace. One of the surfaces of each rod was jDolished 
and etched, and the rod was subjected to reyersals of stress by bending, so that the 
polished surface was alternately extended and compressed. This was done, as in 
Wohler’s original experiments, by making the rod project from a reyohung shaft with 
a load on the ju’ojacting end. As the process went on the rod was from time to time 
examined under the microscope, and in seyeral cases j^hotographs of the same ciystals 
were taken at each stage to record the progressive effect of repeated reyersals of stress. 
Ewing and Rosenhain, “The Cry.stalline Structure of Aletals” (Bakeriau Lectiue, 1899), ‘Phil. 
Trans.,’ A, vol. 19.3, j). 3.53. 
