iC 
May 5, 1923] 
NATURE 
619 

roblem before he left Perth on his homeward journey. 
In his own words, “ it was a severe disappointment to 
me, that the many delays, wholly beyond our control 
. . . prevented me from carrying out this plan.” (The 
plates have since been measured, and, as was an- 
nounced in Nature of April 21, p. 541, the results con- 
firm Einstein’s prediction.) 
It was intended that the large-scale photographs 
of the corona obtained at Wallal, and by the Adelaide 
dition at Cordillo Hills, should be compared for 
evidence of motion within the coronal streamers, 
during the interval of 35 minutes between the times 
of totality at the two stations. The very quiescent 
solar conditions at the time did not hold out very 
good prospects, as Dr. Campbell states, but probably 
the high quality of the negatives will on closer ex- 
amination lead to positive results. er 
All the spectroscopic results of the corona indicated 
alsoa lowactivity of the sun, the coronal lines being very 
much fainter than those recorded in the eclipse of 1918. 





GENERAL discussion on the subject of alloys 
presenting a high resistance to corrosion was 
held on April 13 at the University of Sheffield, the 
meeting being arranged jointly by the Faraday Society, 
the Sheffield Section of the Institute of Metals, and 
the Manchester Metallurgical Society. Sir Robert 
Robertson, president of the Faraday Society, occupied 
the chair. In his opening remarks the chairman 
referred to the economic loss involved in the corrosion 
of steel, and to the great step in advance represented 
by the introduction of stainless steel. In the chemical 
industry, the use of high-silicon irons had proved to 
be of great value. It was important to remember 
that the order of resistance of materials might be 
quite different towards different reagents, so that in 
nitration, for example, while iron and steel would 
resist the action of the concentrated acids, the same 
solutions after being deprived of their nitric acid 
would cause attack. The time was ripe for a general 
survey of the subject. : : 
Prof. C. H. Desch, while noting that no theoretical 
paper was to be presented at the meeting, remarked 
that the study of corrosion had undergone a profound 
change in recent years. lormerly, the usual method 
of experiment was the determination of loss of weight 
of specimens under more or less arbitrary conditions, 
coupled sometimes with measurements of electrolytic 
potential. The first method gave purely empirical 
results, whilst the second was difficult to interpret, 
and the resistance of different metals and alloys often 
appeared to be quite incompatible with their positions 
in the electrochemical series. Gradually, investigators 
had become convinced that the physical character of 
the products of corrosion was a most important factor 
in the process. A metal which from its electro- 
chemical position might be expected to corrode 
rapidly might in the early stages become coated with 
a protective film, after which the action was negligible. 
It was not only films of perceptible thickness that 
exerted such an influence. Recent work had shown 
the importance of films of oxygen and other substances, 
one atom or one molecule thick, to which no definite 
formula could be assigned, but they altered entirely 
the chemical character of the surface. It is still 
impossible to predict the composition of highly 
tesistant alloys, and we have to be content with 
empirical trials, such as have led to the discovery of 
the alloys to be described. The theory of the subject 
is still imperfect, and he urged that more attention 
should be given to the fundamental work of Faraday, 
the neglect of whose teaching was responsible for much 
confusion of thought on the subject of corrosion. 
NO. 2792, VOL, 111] 
The absence of prominences, the smallness of the 
corona and its faintness, all tended to make the 
eclipse a dark one, thus favouring ideal conditions for 
the Einstein plates to secure as many star images as 
possible. 
There is little doubt that when the complete results 
of the Crocker Eclipse Expedition come to be pub- 
lished they will contain a valuable record of the work 
accomplished during the brief interval of five minutes 
fifteen and a half seconds. 
Perhaps one may be permitted to take this oppor- 
tunity of congratulating Dr. Campbell not only on 
the success of this expedition which he so ably led, 
but also on his election in January last to the 
presidency of the University of California. While 
this position will involve great responsibilities and 
absorb much of his time, he will still, fortunately, 
retain his directorship of the Lick Observatory and 
his residence on Mount Hamilton, and he will return 
there on all available occasions. 
Alloys Resistant to Corrosion. 
Three main classes of alloys were dealt with by the 
readers of papers, namely, the stainless steels, the 
alloys of nickel with chromium, and the alloy known as 
Monel metal. Dr. W. H. Hatfield gave an account of 
the extensive series of laboratory tests made in the 
Brown-Firth Laboratory, in which many specimens 
were exposed to the action of simple and mixed 
electrolytes, the results being recorded numerically 
and by means of colour photography. The high 
resistance of the alloys of iron with chromium and 
varying amounts of carbon, known as stainless steels, 
was very evident from these experiments. This class 
of steels was described in detail by Mr. J. H. G. 
Monypenny. The greatest resistance to corrosion in 
these steels is obtained by quenching in such a way 
as to obtain a homogeneous martensite, while the 
attack by reagents is greatest when the steels are 
annealed so as to bring about the greatest separation 
of the carbide and the ferrite. This is in accordance 
with the known effects of galvanic action. Tempering 
at such a temperature that the internal stresses are 
relieved, but coalescence of the carbide is avoided, 
does not lessen the resistance. With a very low 
carbon content, nearly all the chromium is in solid 
solution, so that the steels are resistant even in the 
unhardened state, and this property has led to many 
new uses for the metal. The retarding effect of 
colloidal substances on corrosion is shown by the fact 
that while a properly hardened stainless steel is not 
attacked by vinegar or lemon juice, pure acetic or citric 
acid of the same concentration produces a marked 
attack. The same alloys are highly resistant to the 
action of air at high temperatures or of superheated 
steam. 
It is for their resistance to these agents that the 
next series of alloys, those containing nickel and 
chromium as their principal constituents, are specially 
valued, and these alloys were described by Mr. J. F. 
Kayser. The technical alloys contain iron, and the 
useful compositions are limited to a comparatively 
small area on the ternary equilibrium diagram, 
although some experiments have been made with 
alloys outside that range. Copper is occasionally 
added when resistance to acids is required, but is 
detrimental when high temperatures are involved. 
Aluminium has a remarkable hardening effect, owing 
to the formation of the very hard and infusible 
compound NiAl. Wires for electric furnaces, case- 
hardening boxes, and reaction vessels for ammonia 
synthesis, are among the uses to which this group of 
alloys has been put. The corroding action of furnace 
gases containing sulphur compounds is due to the 
