248 
IN MEMORIAM : HENRY CLIFTON SORBY. 
to review in detail Sorby's works. A nearly complete biblio- 
graphy, in the compilation of which he himself assisted, is pub- 
lished in the " Naturalist," and it will be seen how versatile were 
his talents and how wide was the range of his interests. There 
is scarcely any department of science but owes to Sorby's genius 
some brilliant and fructifying idea or some beautiful and in- 
genious method of research. To chemistry he contributed his 
first paper and to geology his last, but physics, botany, zoology, 
sanitary science, forensic medicine, meteorology, metallurgy, 
mineralogy all received important contributions. 
To geologists the name of Sorby will always stand 
associated with the foundation of the science of microscopic 
petrology. 
Though the investigation of the optical properties of minerals 
by means of thin sections of crystals had been carried on long 
before his time, it was by Sorby that similar methods were 
applied to thin sections of rocks. The art of grinding sections 
of hard substances such as bones, teeth, fossil corals, and the 
like had long been practised, and having learned from the late 
Professor W. C. Williamson, who was an adept, the methods, 
Sorby applied them to the preparation of rock sections ; but, 
for the successful study of his slices new optical appliances were 
required, and these he designed and adapted to the microscope. 
Sorby's first rock section, a photo-micrograph of which is 
appended hereto (Plate XXVII., Fig. 1, and Plate XXVIII., 
Fig. 1.), is little inferior to the work of the English professional 
section cutters of to-day. 
The first product of his new method was a paper contributed 
to the Geological Society of London in 1850 on the Microscopical 
Structure of the Calcareous Grit of the Castle Rock at Scar- 
borough, and it is interesting to us to note that in the Pro- 
ceedings of the West Yorkshire Geological Society for the follow- 
ing year* an amplification of this paper was issued with the first 
illustrations of minute rock structures ever published. Sorby 
followed this up with detailed studies of sedimentary and other 
rocks and investigations of the mineralogical constitution of 
calcareous organic structures, a very important subject to which 
Vol. 111., pp. 197-206 and Plate IV. 
