438 
NATURE 
[Jone 17, 1915 

such a publication is produced. The publishers, in a 
special note, direct attention to these difficulties, and 
say that the Astronomical Society of France, 
confident in the triumph of right and of civilisation, 
pursues, by the publication of this monthly Bulletin, its 
work of instruction and scientific propagation with 
untiring energy, and counts on its adherents to forward 
at once their subscriptions for the current year. The 
two issues mentioned above contain numerous com- 
munications of interest, among which may _ be 
mentioned the first observations of the transit of 
Mercury, an episode in the life of Frangois Arago, 
an address by Monsieur C. Flammarion, delivered at 
the annual general meeting of the Society on April 11 
of the present year, and a summary by Comte de la 
Baume Pluvinel, at the same meeting, of recent dis- 
coveries in astronomy. The application of selected 
filters to the study of Comet Delavan is described by 
Mentore Maggini, being a summary of a research he 
undertook in the year 1913. 

IRON, CARBON, AND PHOSPHORUS. 
R. J. E. STEAD’S knowledge of iron-carbon- 
phosphorus compounds is so remarkable, and 
indeed so unique, that the recent meeting of the Iron 
and Steel Institute in London was rendered memor- 
able by his presentation of a most illuminating paper 
on this subject. As a matter of fact, the word 
‘paper’? is an inadequate description of the publica- 
tion, which is very composite in character and deals 
with some ten aspects of the iron-carbon-phosphorus 
equilibrium; most of them practical, some of them 
purely scientific. 
The constitutional diagram of the iron-carbon- 
phosphorus alloys is not yet completely known. The 
studies of Stead, Wiist, and Goerens have established 
with sufficient accuracy the liquidus fields of that 
. part of the triangular diagram the corners of which 
are represented by iron, iron phosphide, Te,P, and 
iron carbide, Te,C. The compositions of the three 
“binary eutectics’’ are known, as is also that of the 
ternary eutectic, which contains 9119 per cent. of 
iron, I'92 per cent. of carbon, and 6°89 per cent. of 
phosphorus, and freezes at about 950° C. But, in 
spite of the fact that the paper under notice contains 
much new and interesting information about some 
of the solid phases and their relations between the 
solidus and the ordinary temperature, we are still 
without accurate knowledge of the composition of 
most of them and their variation with varying tem- 
perature. The constitutional diagram below the 
solidus has still, for the most part, to be determined, 
and until this has been done the interpretation of a 
good many of Dr. Stead’s results can only be 
provisional. 
In some earlier experiments Dr. Stead squeezed a 
portion of the ternary eutectic out of grey Cleve- 
land iron by pressurg. The amount extruded, how- 
ever, was only a small fraction of the total quantity 
present, for the mould was not maintained, as it 
would have had to have been, at a temperature just 
above the freezing-point of the eutectic. It appears, 
however, that the requisite temperature and pressure 
conditions are realised in the formation and very slow 
cooling of the so-called ‘‘blast furnace bears.” These 
are accumulations of grey iron which gradually form 
underground below the well or crucible of the furnace, 
and sometimes attain an enormous size. One 
of these dug out from beneath one of the Skinningrove 
furnaces weighed between 500 and 600 tons. The cir- 
cumferential contraction of this large mass on cooling 
compressed the central portion, which was the last to 
freeze. According to Dr. Stead, ‘‘the effect of this 
NO. 2381, VOL. 95| 



enormous pressure caused the central plastic mass to 
assume a vertical column, an arrangement closely 
resembling on a small scale the basalt of Giants’ 
Causeway.’’ These columns could be separated from 
one another. Chemical analyses indicate that about 
go per cent. of the phosphorus originally present had 
been extruded vertically between the columns during 
the period of intense compression. A “bear” with a 
similar columnar structure has also been found in the 
hearth of a Cleveland furnace of Messrs. Bolckow, 
Vaughan and Co. at Eston. Here, too, the columns 
were all vertical, and varied from § to in. in 
diameter, and in some places were so loosely attached 
to each other that they could be separated by hand. 
These also were found to be low in phesphorus. In 
the case of a bear under an Ormesby furnace which 
had been in blast some thirty-eight years, about two- 
thirds of the original phosphorus had been removed, 
but there were no indications of columnar structure. 
On the other hand, the metal found in the hearth of 
one of the furnaces at Ferryhill consisted of columnar 
crystals of iron saturated with iron phosphide, with 
walls of iron phosphide, but entirely free from carbon 
and’ silicon. Here, therefore, the conditions must 
have been much more oxidising, and no_ ternary 
eutectic was present. It is, however, abundantly clear 
that by far the greater part of the phosphorus in highly 
carbonised iron is concentrated in the last portions 
which freeze. 
Two photographs reproduced in Dr. Stead’s paper 
illustrate the structure and mode of occurrence of the 
ternary eutectic extremely well. Both were developed 
by heat-tinting, iron phosphide appearing blue or 
purple, iron carbide red, and iron saturated with 
phosphide white. No. 1 is termed by Dr. Stead 
the ‘‘normal”’ structure, and is clearly lamellar, 
recalling the well-known pearlite in its form; 
No. 2 is evidently that of a very slowly cooled speci- 
men, the lamellae having coalesced to qn appreciable 
extent. 
The equilibrium relations between iron, iron carbide, 
and iron phosphide in the range of temperature 
ro00° C. to 7oo° C. are of the utmost importance in ~ 
the light they shed on the so-called ‘‘ ghosts’ or 
““phantoms,’’ which are very liable to occur in large 
forgings of mild or medium steel. These are lines or 
streaks which can only be detected after rough turn- 
ing. As the names indicate, they are not deep-seated. 
They are completely removed by turning off a thin 
layer of the steel, but are liable to reappear in other 
places. It is clear, therefore, that they are very 
attenuated and irregularly distributed. The usual 
view held is that they are harmful, and forgings are 
sometimes rejected on account of their presence, in 
spite of the undoubted fact that some of them have 
proved satisfactory in service even though such ghost 
lines were present. Their occurrence, in Dr. Stead’s 
view, is due to the fact that “in steels containing 
045 per cent. and less carbon, although the carbon 
may be equally distributed when the steel is at 
to00° C., on very slow cooling the ferrite first appears 
in the parts richest in phosphorus. The portions which 
are partially saturated with phosphorus cannot so 
readily hold in solid solution at certain temperatures 
as much carbon as the surrounding portions which 
contain little or no phosphorus; consequently, when in 
cooling it reaches these temperatures, the carbon 
diffuses out of the phosphorised parts into the sur- 
rounding pure metal.’’ These areas of phosphide con- 
centration constitute the ghosts, and, as sulphides and 
phosphides segregate together, sulphides are generally 
present in them as well. 
Dr. Stead has succeeded in producing typical ghost 
lines synthetically by heating to 1000° C. strips of soft 
Bl 
