Henry Clifton Sorby

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(b. Woodbourne, near Sheffield,England, 10 May 1826; d. Sheffield. 10 March 1908)

microscopy,geology, biology, metallurgy.

Most of Sorby’s ancestors since the seventeenth century had been middle-class cutlers in Sheffield. His father, Henry Sorby, owned a small cutlery factory; his mother was the daughter of a London merchant. Sorby attended local schools and at age fifteen he won, as a prize for mathematics, a book entitled Readings in Science, published by the Society for Promoting Christian Knowledge (first edition 1833), which set the direction of his life. During the next four years he completed his education with a full-time private tutor, the Rev.Walter Mitchell, a competent scientist who later wrote on crystallography and mechanical philosophy in the popular compendium Orr’s Circle of the Sciences. Sorby attended no university-he later said that he planned his education “not to pass an exam but to qualify myself for a career of “original investgation.” Closely tied to his mother, he never married. He inherited a modest fortune after his father’s death in 1847 and thereafter devoted himself entirely to science while continuing to live in Sheffield, a flourishing steel manufacturing town somewhat limited intellectual resources. Sorby became very active in the local Literary and Philosophical Society, which had fortnightly discussions on a wide range of subjects and provided him with diverse intellectual stimulation and the opportunity for both leadership and service that he could not have obtained as a young man in a metropolis.

Isolated from the most active scientific circles, Sorby worked quietly on unfashionable topics in a laboratory in his own house. Cast in much the same mold as many other English country gentlemen whose education, isolation, and leisure enabled them to make original observations, he initiated two major areas of science– and carried neither to the point of maturity. Often called an amateur, he was one only in the sense that he was not working in an institutional environment or at the expense of anyone else. He was, in fact, a full-time independent research scientist at a time when were few such.

Sorby’s most influential scientific work was done between 1849 and 1864 on the application of the microscope to geology and metallurgy. In both fields his work had a certain elegance derived from a mixture, in about equal proportions, of simple quantitative observation, meticulous new experimental technique, and novel interpretation based on the application of elementary physicochemical principles to complex natural phenomena. “My object,” he said in his last paper, “is to apply experimental physics to the study of rocks.” His most famous achievement is the development the basic techniques of petrography, using the polarizing microscope to study the structure of thin rock sections. The geological conclusions that Sorby drew from such studies were of utmost importance. He started this work in 1849 with studies of sedimentary rocks. In 1851 he became involved in a widely noticed debate on the origin of slaty cleavage, and in an 1853 paper he showed conclusively that cleavage was a result of the reorientation of particles of mica accompanying the deformation (flow) of the deposit under anisotropic pressure, Sorby later studied organisms in limestibe abd discovered the presence and Significance of microorganisms in chalk. In a paper published just before his death (1908) he returned to sedimentation and summarized his whole approach.

Sorby first studied the rate of settling and angle of repose of sand and silt particles in still and turbulent water, and the transport of grains along the bottom by currents of various velocities; then, observing bedding angles, ripple marks, and the variation of particle size with depth (with porosity measurements to allow correction for compaction, solution, or compression of strata) in actual sandstones, he deduced rather precisely the conditions under which the sediments had been deposited.

From slate Sorby moved to schists and metamorphic rocks in general. Of great importance was his 1858 paper on liquid inclusions in crystals,both natural and artificial. Inclusions in large crystals also had been observed by David Brewster and Humphry Davy in the 1820’s, but Sorby used the microscope to find abundant smaller ones within the microcrystals in many metamorphic rocks. He measured the size of the bubbles that resulted from liquid shrinkage after the cavity had been sealed,and he performed laboratory experiments to measure the expansion of liquids in sealed tubes under pressure that enabled him to deduce the temperature and pressure at which the rocks had been formed. This information revealed large differences in the temperature of formation of granites from various localities and led Sorby to realize the great role played in rock formation by water-bearing magma at high temperature and pressure. (In 1863, after further experiments, he wrote: “Pressure weakens or strengthens chemical affinity according as it acts against or in favour of the change in volume”— a clear anticipation of Le Chatelier’s principle.) The 1858 paper was illustrated with 120 drawings made under the microscope at magnifications between 60 and 1,600, transferred to the lithographer’s stones by Sorby himself. He concluded: “There is no necessary connection between the size of an object and the value of a fact, and...though the objects I have described are minute the conclusions to be derived from the facts are great.”

There were still eminent geologists who saw little good to come from studying mountains with microscopes, and Sorby’s work was rather slow to be widely appreciated. He was not one to wring the last shred of meaning from a topic, however; and it was fortunate for geology that while touring the Rhine valley with his mother before a conference in the summer of 1861, he met the young geology student Ferdinand Zirkel (1838–1912), whom he inspired to take up the new methods. Zirkel did so with Germanic thoroughness, and his two—volume Lehrubuch der Petrographie (1866) established petrography as a broad and systematic science.

In 1863–1864 Sorby turned briefly from rocks to metals. Although he began with a general interest in the structure of meteorites (the only metallic bodies to have an easily visible crystalline structure), the principal stimuli seem to have been two evenings at the Literary and Philosophical Society during which ornamental etching and the manufacture of iron and steel were discussed—combined, of course, with the omnipresence of these metals in his native city. On 28 July 1863 he recorded in his diary, “Discover the Widmannstättischm structure in iron.” Circle-L was the brand mark of the Swedish wrought iron preferred over all others by Sheffield steelmakers for conversion to blister steel,(Sorby was probably using a piece that had already been converted to steel and had large grains containing easily visible plates of iron carbide. The iron itself, being free from carbon, could not have had a true Widmannstätten structure.) Always somewhat of a showman, Sorby prepared six different samples to display under the microscope at a soirée of the meeting of the British Association at Newcastle in August, by which time he had already identified in steel three separate crystalline compounds that differed in their reaction to nitric acid.

Early in 1864 Sorby recorded his structures by nature printing, an old and simple process in which a relief-etched surface was inked and pressed to paper. A superb print showing the structure in the Elbogen meteorite made by Aloys von Widmannstätten and Karl von Schreibers in 1813 had inspired later ones of which Sorby knew; but before 1863 the etching of terrestrial irons was done only decoratively or to reveal gross texture, not microstructure.

Sorby worked with a local photographer to make several photomicrographs of steel, which he showed and discussed at the British Association meeting in September 1864. This paper was the true foundation of metallography, although it was published only in abstract. Sorby mentions “various mixtures of iron, two or three well-defined compounds of iron and carbon, of graphite and of slag; and these, being present in different proportions, and arranged in various manners give rise to a large number of varieties of iron and steel.” Despite considerable interest at the time, no one followed this start. There was no Zirkel of metallurgy, and Sorby himself moved on to other fields, not returning to steel until 1882 and not publishing anything in detail until 1885. By that time interest in metal structure had been aroused by papers by Chernoff (1868, 1879), Martens (beginning in 1878), and Osmond (1885), none of whom knew Sorby’s earlier work. Sorby’s 1885 paper was circulated in preprint form, but final publication was delayed for two years by a search for suitable photogravure methods.

In the meantime Sorby had shown, by the use of higher magnifications, that the feature that he had earlier called the “pearly constituent” because of its iridescence was an extremely fine duplex lamellar mixture of iron and iron carbide resulting from the decomposition on slow cooling of a constituent that was stable at high temperatures. Earlier he had identified graphite and iron oxide in iron samples and had described the true nature of recrystallization and transformation: “Iron and steel are not analogous to simple minerals, but to complex rocks.” The structural origin of many age—old differences between various kinds of iron and steel was now clear. After 1885 people in many countries took up the new field. By 1900 a range of structures had been observed in many alloys and cataloged in relation to composition and heat treatment, and a beginning was being made in the application of thermodynamics to the study of alloys and of the effects of mechanical deformation.

The interest that supplanted metals and meteorites in Sorby’s mind in 1864 was spectrum analysis. Four new elements had been discovered by emission spectroscopy since Bunsen and Kirchhoff’s announcement of 1860. G. G. Stokes described the use of absorption spectra for identifying organic substances in March 1864, and Sorby at once saw a new application for his favorite instrument. Quickly developing the necessary combination of microscope and spectroscope, he first examined minerals in rock sections, then moved on to study the coloring matter in animal and plant tissues. Carotene was one of the discoveries, and his work on chlorophyll. autoymn colors, and blood identification aroused popular interest, the last involving him in a famous murder trial in 1871. Sorby’s observation of unrecorded lines in the absorption spectrum of the mineral jargon (jargoon) led him to announce, in March 1869, the discovery of a new element that he named jargonium. He became involved in an unpleasant priority dispute and more embarrassment when, six months later,he had to retract, for he had found that the lines were due to uranium. Also in 1869 he used his microspectroscope to study the color of borax beads, thus refining an old, and at the time very important, method of mineral analysis.

After his mother’s death in 1874 Sorby widened his activities. He frequently traveled to London for scientific meetings, became a member of the Council of the Royal Society, and was elected president of several societies: the Royal Microscopical Society in 1874, the Mineralogical Society (of which he was the first president) in 1876,and, in 1878– 1880, the Geological Society of London. Although he continued to conduct his own research purely personal basis, he became increasingly concerned with public policy in support of science. Sorby advocated separation of research and teaching, and in the contribution “On Unencumbered Research—A Personal Experience,” to Essays on the Endowment of Research (1876), edited anonymously by Charles Appleton for a group of scientists at Oxford, he used his own work as an example of the value of unencumbered and undirected—but not isolated—research. In 1871 he had discussed the possibility of endowing a Royal Society professorship in experimental physical research that would be free from teaching duties. In 1874 he planned a marine biological research station that he proposed to endow and direct; but when one was established ten years later by the Royal Society, he was not asked to participate either financially or scientifically. This was apparently the result of a quarrel with Cambridge biologists including Alan Sedgwick (great-nephew of the geologist of the same name), whose intolerant antireligious attitude disgusted him. Though a revolutionary in science, Sorby was a pillar of the Church of England and very conservative in general outlook.

Sorby’s public activities thereafter assumed a more local focus. Beginning in 1880, he worked to promote the formation of Firth College in Sheffield and served as its president from 1882 to 1897. In 1897 University College was formed in sheffield by the amalgamation of Firth College with the local technical and medical schools. Despite his international reputation, Sorby was not a great enough local figure to be chosen as its president, and he noted in his diary that he was “a trifle disappointed at being thus superseded after so many years of work.” He was appointed vice-president of the college, however, and his research continued. He had bought a thirty-five-ton yawl, carrying a crew of five, in 1878 and had equipped it as a floating laboratory. Thereafter he spent five summer months of almost every year until 1903 cruising off the east coast, studying marine biology and geology but also developing new interests, especially architectural history based on a close study of brick dimensions and construction details in Roman, Saxon, and Norman buildings in East Anglia. History and archaeology remained at the level of serious hobbies, however, and Sorby did not carry them to the point of professional publication. He undertook important studies on temperatures and on silt and sewage movements in the Thames estuary for the Royal Commission on the Thames. For some years, marine biology was his dominant interest. This work has not been critically evaluated by historians, but it seems that his only lasting contribution was the technique he developed in 1889 for differentially staining biological tissues and mounting soft-bodied animals as permanent lantern slides for demonstration and study.

Sorby became lame in 1902 and suffered partial paralysis after an accident in 1903 that confined him virtually to his room. For the next five years he worked over the notes that he had accumulated throughout his life, returning to the geology that had begun his career and that resulted in a last major, although retrospective, paper on sedimentary rock formation. It was read at the meeting of the Geological Society of London on 8 January 1908, two months before his death.

In his will Sorby left some journals and £500 to the Literary and Philosophical Society, but his main bequests were to the University of Sheffield for the establishment of a professorship and a research fellowship, the latter under the control of the Royal Society. The bulk of his library also went to the university.


I. Original Works. The library of the University of Sheffield has Sorby’s diary, containing terse daily entries for 1859–1908 (except for most of 1871–1882, 1894–1895. and 1903–1905) and a 2–vol. bound assembly of his printed papers and notices. A collection of letters to Sorby from many correspondents is in the Sheffield Central Library, Cat. no. SLPS 51. The metallurgy and geology departments of the University of Sheffield have preserved many of Sorby’s original microsamples of rock and steel, the earliest bearing the date 1849. Many of his magnificent preparations of marine animals are in the zoology department.

Sorby wrote no book. G. H. Humphries, “A Bibliography of Publications—H, C. Sorby.” in C. S.Smith, ed., The Sorby Centennial Symposium on the History of Metallurgy (New York, 1965). 43–58, contains 233 entries. The most important of these are “On the Origin of Slaty-Cleavage,” in Edinburgh New Philosophical Journal, 55 (1853), 137–150; “On the Microscopical Structure of Crystals Indicating the Origin of Minerals and Rocks,” in Journal of the Geological Society, 14 (1858). 453–500; “Bakerian Lecture. On the Direct Correlation of Mechanical and Chemical Forces,”in Proceedings of the Royal Society,12 (1863), 538–550: “On a Definite Method of Qualitative Analysis of Animal and Vegetable Colouring Matters by Means of the Spectrum Microscope,” ibid., 15 (1867), 433–456; “On Unencumbered Research-A Personal Experience,”in Essays on the Endowment of Research (London, 1876),149–175); “The Application of the Microscope to Geology, etc. Anniversary Address of the President,” in Monthly Microscopical Journal, 17 , (1877) 113–136: “On the Structure and Origin of Limestone,” in Quarterly Journal of the Geological Society of London,35 (1879) 56–95; “On the Application of Very High Powers to the Study of the Microscopical Structure of Steel” in Journal of the Iron and Steel institute, 31 (1886), 140–144; “The Microscopical Structure of Iron and Steel,” ibid., 33 (1887), 255–288; “On the Preparation of Marine Animals as Lantern Slides to Show the Form and Anatomy,” in Transactions of the Liverpool Biological Society, 5 (1891), 269–271; “Fifty Years of Scientific Research,” in Annual Report of the Sheffield Literary and Philosophical Society(1898), 13–21; and “On the Application of Quantitative Methods to the Study of the Structure and History of Rocks,”in Quarterly Journal of the Geological Society of London,64 (1908).171–233.

II. Secondary Literature. The only complete biolographical Study is Norman Higham. A Very Scientific Gentleman. The Major Achievements of Henry Clifton Sorby (Oxford, 1963). Obituary notices with more than usual perception are J. W. Judd, “Henry Clifton Sorby, and the Birth of Microscopical Petrology,”in Geological Magazine, 5th ser. 5 (1908), 193–204; and Archibald Geikie, “Henry Clifton Sorby, 1826–1908,”in Proceedings of the Royal Society. B80 (1908). Ivi-lxvi; and W. J. Sollas, “Anniversary Address of the President,” in Proceedings of the Geological Society (London), 65 (1909), I–Ivii, Shortly before Sorby’s death Geikie had discussed nineteenth-century achievements in petrology as part of his anniversary address as president of the Geological Society —Transactions of the Geological Society of London,64 (1908), 104–111—which presents Sorby’s great impact on geology from a contemporary viewpoint. See also George P. Merrill. “The Development of Micro-Petrology,”in The First One Hundred Years of American Geology (New Haven, 1924),643–647.

For later analyses, see W. H. Wilcockson, “The Geological Work of Henry Clifton Sorby,” in Proceedings of the Yorkshire Geological Society, 27 (1947),1–22; and G. H. Humphries, “Sorby: The Father of Microscopical Petrography” in C. S. Smith, ed.. The Sorby Centennial Symposium on the History of Metallurgy (New York. 1963), 17–41. This centennial volume depicts the changes in metallurgy following Sorby and contains other comments on Sorby himself by the editor (ix-xix) and N. Higham (1–15). Sorby’s metallurgical contributions also were analyzed by C. H. Desch in his 20–page pamphlet The Services of Henry Clifton Sorby to Metallurgy (Sheffield, 1921); and by C. S. Smith in “Metallography in Sheffield,” ch. 13 of his A History of Metallography (Chicago, 1960). Records and memorabilia of Sorby are described by A. R. Entwisle, “An Account of the Exhibits Relating to Henry Clifton Sorby....” in Metallography 1963, Special Report no. 80, Iron and Steel Institute (London, 1964). 313–326. A rather personal view of the role of microscopic petrography in the broader science of rocks is given by F. Y. Levinson-Lessing. Vvedenie v istoriyu petrografii (Leningrad, 1936), English trans. by S. I. Tomkeieff as A Historical Survey of Petrology (Edinburgh-London, 1954).

Cyril Stanley Smith

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Sorby, Henry Clifton (1826–1908) An English amateur scientist, Sorby studied estuarial and inland waters of England, but he is best known for developing the study of roċks in thin sections, using the techniques invented by Nicol. He was the first to show that individual mineral crystals and grains could be identified using this process. He also used the method to study meteorite sections.