Ix Obituary Notices of Fellows deceased. 
conclusion was erroneous, and that the peculiar spectra belonged to some 
compounds of the oxides of uranium with zirconia. With characteristic 
frankness he at once published an acknowledgment of the mistake.* 
From the investigation of the microscopic structure of terrestrial rocks 
Sorby was naturally led to enquire into the structure and probable history of 
those masses of mineral matter which come to us from outer space in the 
shape of meteorites. He soon found that the olivine enclosed in these stones 
contains excellent “glass-cavities,” proving that it was once in a state of 
igneous fusion, likewise “ gas-cavities,’ like those so common in volcanic 
minerals and indicative of the presence of some gas or vapour. He ascer- 
tained that the minerals in meteorites, usually considered to be identical 
with those in terrestrial volcanic rocks, nevertheless present some character- 
istic differences in structure. When he turned to the siderites and siderolites 
or iron-meteorites, he soon saw that in order to gain an insight into their 
structure and probable origin it was desirable first to study various artificial 
irons. In this research he ascertained that certain microscopic structures 
very closely similar to those in some varieties of meteorites, could be 
artificially produced. He was thus enabled to indicate, as far back as 1864, 
how much may be learnt as to the structure and composition of different 
types of artificial iron by the aid of the microscope. Notwithstanding the 
obvious practical importance of his observations and conclusions in relation 
to the development of our iron industry, they attracted no attention. At 
last, after some twenty years, the matter was taken up seriously in 1887 by 
the Iron and Steel Institute. Sorby was then requested by that Society to 
consider, together with Dr. John Percy and Sir Henry Bessemer, the best 
way of illustrating a complete paper on the subject. “In those early days,” 
he remarks, “if a railway accident had occurred, and I had suggested that 
the Company should take up a rail and have it examined with a microscope, 
I should have been looked upon as a fit man to send to anasylum. But 
that is what is now being done. What I really proved was that various 
kinds of iron and steel are varying mixtures of well-defined substances, and 
that their structure is in many respects analogous to that of igneous rock 
I also took specimens of iron and steel and acted upon them with acid, 
so that it was possible to print from them as from types, and show many 
interesting points connected with their structure.” Sorby continued his 
investigation and published various papers on the subject during the 
following decade. He is now recognised as the great pioneer in micro- 
metallography, and his methods have proved of great practical use in the 
manufacture and testing of iron and steel. As a mark of this recognition one 
of the most important constituents of steel has been named after him, Sorbite. 
One of Sorby’s most useful inventions to which he was led in 1865 by 
his study of meteorites is the spectrum-microscope.t He applied this 
* ‘Roy. Soc. Proc.,’ vol. 17, p. 511, and vol. 18, p. 197. 
+ It was fully described, together ae its method of use and its application, in ‘ Roy. 
Soc. Proc.,’ vol. 15 (1867), pp. 483-455. 
