Vol. IX.] 
[Part II. 
PROCEEDINGS 
OF THE 
YORKSHIRE 
GEOLOGICAL AND POLYTECHNIC SOCIETY. 
Edited by JAMES W. DAVIS, F.S.A., F.G.S., &c. 
1886- 
OX SOME REMARKABLE PROPERTIES OF THE CHARACTERISTIC CON- 
STITUENT OF STEEL, BY H. C. SORBY, ESQ., LL.D., F.R.S. 
The microscopical examination of suitably prepared specimens 
of iron and steel with moderately high magnifying powers shows 
that there are two very well marked constituents. One of these 
is comparatively soft, and is undoubtedly iron free from carbon. 
The other is intensely hard, and most probably contains combined 
carbon, since it occurs in white cast iron, blister steel and other 
varieties known to contain carbon in that state. Independant of 
these there is obviously another constituent which has microscopi- 
cal characters entirely unlike those of the others, and gives 
beautiful colours like mother of pearl. For this reason I have 
always called it the pearly constituent. Laterly I have made use 
of very much higher magnifying powers, and find that with 
an illuminator contrived some years ago by the late Richard 
Beck, a power of 650 linear can be employed with ease. This 
shows that the pearly constituent really has a structure closely 
like that of pearl, being made up of alternating thin plates. 
After very carefully studying most of the leading varieties of iron 
and steel, I have come to the conclusion that these plates are 
alternating layers of soft iron free from carbon, and of the 
intensely hard compound with carbon, already mentioned. The 
