Henry Sorby (1826-1908), the Spectrum Microscope, and Spectra of Various Biological Materials

Research initiated by Henry Clifton Sorby in the mid-19th century produced one of the earliest instrumental analysis techniques that combined two separate technologies to improve on previous spectroscopic methods. The spectrum microscope was built on discoveries and advancements by Henry Hyde Wollaston, Joseph von Fraunhofer, Gustav Kirchhoff, Robert Bunsen, Felix Hoppe-Seyler, and George Stokes, first in identifying the absorption lines present in astronomical observations, then improving the resolution of these bands, finally resulting in the techniques of spectroscopy and spectrophotometry by the mid-19th century. Sorby’s initial work with the spectrum microscope gained him a reputation for then-unique examinations of rocks, minerals, metals, and sediments, obtained by creating thin slices of the materials and reporting their structural and spectroscopic properties. Sorby, an isolated and independent gentleman scientist from a wealthy family, realized that the spectrum microscope methods could also be applied to botanical and physiological materials. Starting in 1865, he published about ten years of papers illustrating the utility of this hybrid instrument, including many results ranging from human blood in various oxidized and reduced states, and those of vegetable dyes, chlorophyll treated with acids and bases, and a variety of flower and wood samples. A review of Sorby’s instrumentation, method, and results for biological materials will be presented.