68 | Great Geologists
founding the science of
During the next few years
sedimentology. He first
Sorby published a series
noticed current-formed
of brilliant papers on the
structures whilst sheltering
petrography of sandstones
from the rain in a quarry in
and limestones, but his
1847. This was at the time
interests also included
that he was researching fluvial
igneous and metamorphic
geomorphology for his first
rocks (for example, he
publication, and he was struck
was the first to describe
by the similarities between
the deformation of ooids
the structures he observed
and crinoid ossicles in
in the rock and those he had
lightly metamorphosed
observed forming in modern
carbonates). He determined
sediments. Over the next
different types of detrital
few years, he systematically
quartz and how this could
observed and described
be linked to sediment
sedimentary structures at
provenance. In his papers
outcrop and conducted flume
on carbonate rocks he
tank experiments at home
described the conversion
Thin-section of a calcareous cemented sandstone. Several different
to understand their genesis.
of aragonite to calcite,
types of detrital quartz grains are present which could be related to
A series of publications
dolomitization, different
different sediment source regions, a notion that Sorby pioneered.
emerged - for example “On
phases of cementation
the structures produced by
and recognized that the
the current present during the deposition of stratified rock”
coccoliths that form chalk are of organic origin. He described
published in 1859, but a full summary of this line of endeavour
many of the constituent grains of carbonate rocks including
was not published until his monumental final paper in 1908,
ooids and a variety of bioclasts.
“On the application of quantitative methods to the study of the
During a visit to Germany in 1860, Sorby met a young German
structure and history of rocks.”. This masterly synthesis of the
geologist named Ferdinand Zirkel who was inspired by the new
hydrodynamic interpretation of sedimentary structures reviewed
science of petrography and applied it systematically to igneous
their relationship with current velocity, the angles of repose of
rocks – the results are summarized in the 1866 publication
different sediments and the settling velocity of grains in water. It
Lehrbuch der Petrographie. By this time Sorby’s interests were
also described soft sediment deformation, the measurement of
already moving on, first to the petrography of meteorites and
porosity and the exact determination of structural deformation.
then to man-made metals.
The use of fluid inclusions in minerals to understand the
Sorby recognized that metals had a crystalline structure and
temperature of crystallization is now a well-established
the composition of steel could be determined by microscopic
technique in a variety of geological studies. Sorby was, once
examination once it had been etched by acid. His understanding
again, a pioneer in developing this technique, publishing a key
of the composition of steel and what gave it its strength
paper “On the microscopical structure of crystals, indicating the
revolutionized its manufacture. He later remarked “In those early origin of minerals and rocks” in 1858.
days, if a railway accident had occurred and I had suggested that
In 1878, Sorby purchased a yacht, The Glimpse. He had it fitted
the company should take up a rail and have it examined under
out as a floating laboratory and, over a series of twenty-five
the microscope, I should have been looked upon as a fit man to
summers, proceeded to survey the eastern coast of England,
send to an asylum. But that is what is now being done.”
carrying out studies on coastal sediments and marine fauna. His
Parallel to his petrographic studies, Sorby was engaged in
intellectual curiosity seems to have been boundless. In 1892,
a number of other lines of geologic research. Perhaps the
he walked 1,200 miles in four months (aged 66) studying and
most important of these was the recognition of sedimentary
describing ancient buildings for his archaeological research.
structures as indicators of past deposition processes, thereby