258 Mr. G, T. Beilby on the Hard 
corpuscles, while the carriers of the positive leak are particles 
of molecular dimensions. 
These experiments were carried out at the Cavendish 
Laboratory during the earlier months of this year, and, 
in conclusion, I wish to express my sincere thanks to 
Professor Thomson for his kindly interest and for many 
valuable suggestions while the experiments were in progress. 
Christ’s College, May 10th, 1904. 
XXVII. The Hard and Soft States in’ Metals. 
jy Aa, 1, BEILBY:*. 
[Plates V.-IX.] 
Introductory. 
1, HERE does not hitherto appear to have been any 
serious attempt to arrive ata single guiding principle 
which will harmonize the many isolated phenomena of the 
solid state which are met with in the practice of the metal- 
working arts, and in the systematic testing of materials in 
hysical and engineering laboratories. 
2. The hardening and re-softening of metals in annealing, 
forging, rolling, wire-drawing, and stamping, as these are 
practised in the arts; the flow of metals dealt with by Tresca 
and by Spring ; viscosity and elastic fatigue in metals and 
other solids, as observed by Kelvin ; mechanical fatigue and 
disruption in metals exposed to frequent alterations of stress, 
investigated by Wohler, Baker, Bauschinger, Unwin, and 
others ; the deformation of crystalline grains and their resto- 
ration and growth by heat-annealing, studied by Ewing and 
Rosenhain; and the character of distortion and rupture of 
iron and soft steel, recently discussed by Osmond, Frémont, 
and Cartaud—make a sufficiently varied, though far from 
exhaustive list of subjects, which, in spite of much special 
study, still remain in comparative isolation from each other, 
3. Looking broadly over this wide range of subjects, it is 
seen that two complementary phenomena stand out promi- 
nently, round which the others may be naturally grouped. 
(1) The deformation of a metal by stresses beyond the elastic 
limit invariably tends to alter the character of the metal in 
one definite direction—that is, towards a diminished capacity 
for being deformed by such stresses. (2) The plastic quality 
can be restored to the deformed metal by raising it to a 
suitable temperature. 
* Communicated by the Faraday Society. (A paper read before the 
Faraday Society on Thursday, June 9, 1904. 
