NATORE 
[ FEBRUARY 28, 1907 
another at angles that never 
species of crystal. The forms in each set of -in 
organisms and in crystals alike—may be regarded as the 
necessary resultants of the molecular constitution of their 
initial units in the particular media and surroundings in 
which they occur. 
vary for each particular 
cases 
PROPERTIES OF ALLOYS. 
HE research described in the report was carried out by 
the authors with the cooperation of the Broughton 
Copper Co., Manchester, and the British Aluminium Co., 
cae 
After a short annealing. 
Structures of an alloy containing { 
Magnification 150 diameters. 
Milton, who furnished respectively the best commercial 
copper and aluminium for making the alloys, undertook 
the rolling and drawing of the materials, and made special 
castings where necessary. 
The salient points of the report are stated as follows :— 
(a) The number of alloys that have been found of any 
industrial and technical promise is small. Such alloys are 
1 Abstract of the Eighth Report to the Alloys Research Committee : On 
the Properties of Alloys of Aluminium and Copper. By Prof. H. C. H. Car- 
yenter and Mr. C. A. Edwards, of the National Physical Laboratory. 
Read at the Institution of Mechanical Engineers on January 18 
NO. 1948, VOL. 75] 
chiefly those very rich in copper. At this: end of the 
series the limit of serviceable alloys must be placed at 
II per cent. At the other end of the series the limit is 
even smaller. Among the specifically light alloys rich in 
aluminium the limit is probably not higher than 4 per 
cent. of copper. Between 11 per cent. and 96 per cent. of 
aluminium (exclusive) the alloys do not appear to be of 
any practical promise. 
(b) But if the range of serviceable alloys is narrow, their 
quality is certainly high in several instances. ‘This state- 
ment holds for certain of the rich copper alloys contain- 
ing between 7 per cent. and 10 per cent. of aluminium. 
It is not going too far to say that in certain respects the 
Querched from goo’ C. in water. 
90°06 per cent, of copper. 
9790 A aluminium. | 
best of them equal, and even surpass, high-quality steels | 
of the same general character. 
The following summary refers only to the rich copper | 
alloys :— 
(c) Four features of the results of the tensile stress tests 
of outstanding interest merit a special comment. 
(1) In view of the doubt which exists at the present 
time as to whether copper and its alloys possess true 
yield-points, it is important to record that from o-1 per 
cent. to 9 per cent. of aluminium the alloys possess clearly) 
marked yield-points. 
