124 Barrett, Brown, AND Haprreitp—Researches on the 
examination might clear up. From the accompanying report, by Dr. Carpenter, 
it will be seen that our expectation has, to a large extent, been realized. An outer 
layer of nearly pure iron, ferrite, was found in the original rod of the aluminium- 
iron alloy; but this layer had been removed by the act of turning down the 
specimens. . 
The accompanying report from the National Physical Laboratory refers to the 
following specimens, the chemical analyses of which were made in the laboratory 
of the Hecla Steel Works, Sheffield. 
S.C.I. (Swedish charcoal-iron), containing 99°89 Fe, 0:03 C, 0:07 Si. 
1167 H. (Aluminium-iron alloy), 97°33 Fe, 0:24 C, 0°18 Si, 2°25 Al. 
898 K (Silicon-iron alloy), 97:3 Fe, 0:2 C, 2°6 Si. 
Norres ExputANAtorRY OF THE PuHoro-MIcrRoGRAPHS.* 
Prate IX. 
Rod S.CT. 
‘‘Photo-micrographs 1 and 2 represent the structures in different parts of the 
same transverse section. Deeply etched in 1 °/, nitric acid in absolute alcohol. 
‘“¢ Dark area shown in No. 1 about 2 of the total area. [It will be noticed that 
the white patches, ferrite, are fairly uniformly distributed. In the high magni- 
fication of No. 2, hexagonal or polyhedric grains of ferrite are seen. | 
Rod 1167 H. 
‘‘ Photo-micrograph No. 3 (lightly etched) shows the structure as one proceeds 
from the edge (white) to the centre. Ferrite, granular pearlite, and nodules are 
all present; and although the structure is different from that of the ingot, it is 
only such as might be expected from the thermal and mechanical treatinent to 
which the rod has been subjected. Attention is drawn here to the fact that a _ 
layer of ferrite, varying in diameter from about } to . mm., occurs on the 
outside of the rod right round. No. 4 (magnification = 2520 diameters) shows 
small nodules forming a ring pattern on a ground-mass of what in No. 3 is seen 
to be granular pearlite. It seems probable that the nodules are the oxide of 
aluminium. 
* The circles of the micro-photographs represent, of course, only a minute portion of the cross-section 
of the rod. When the micro-photograph is taken at the edge, this word is added. 
