269 Mr. G. T. Beilby on the Hard 
Summary of the Evidence. 
17. The better to preserve the continuity of the argument,. 
the evidence is briefly summarized at this stage, certain 
detailed observations being given more fully at the end of the: 
paper. 
18. The malleable and ductile metals—gold, silver, pla- 
tinum, copper, and lead—are all well adapted for the study of 
the phenomena of hardening and softening. Iron and nickel, 
while they possess the common characteristics in a very marked. 
degree, have other properties which occasionally render their 
behaviour less plain and simple. 
19. The brittle crystalline metals, antimony and bismuth, 
show the phenomena of flow in a peculiarly clear way; and 
their behaviour therefore falls perfectly in line with that of 
the ductile metals. It is therefore of special value in showing 
how flow may take place altogether apart from malleability or 
ductility. 
20. Among the ductile metals silver occupies a fairly 
central position in respect to hardness and tensile strength, 
while its optical, electrical, and thermochemical characters. 
are particularly well marked. I have therefore selected this. 
metal as the most suitable with which to illustrate a summary 
of the evidence in support of my argument. A fuller de-. 
scription of some of the experiments and observations is given 
at the end of the paper, and for convenient reference to this. 
portion the paragraphs have heen numbered throughout. 
The Mechanical Properties of the two Phases in Silver. 
21. When work is done on silver by rolling, hammering, or 
wire-drawing, its hardness and tenacity are raised to a very 
high point. In this way the tensile strength of soft silver may 
be raised from under 10 tons per square inch to over 20 tons.. 
22. A strip of silver-foil may be made so hard and springy 
by hammering, that it might be used as a vibrating tongue 
of a reed instrument, After heating to 260° the hardened 
strip loses all its spring, and becomes so soft that it may be 
pressed perfectly flat on a smooth surface by the slightest 
pressure from the finger. (See par. 64.) 
23. The contrast between the hard and soft phases in silver: 
is greater than that among the different ductile metals when 
these are in the soft phase. Silver in the A. phase is much 
more akin to copper in the same phase than it is to silver in 
the C phase. 
The Micro-structure. 
24. The micro-structure of annealed silver, if the metal is 
in a sufficiently massive form, is always crystalline ;.and con-— 
sists of skeletons or grains built up of lamelle of similarly 
