Henry Thomas Maire Silvertop Witham (1779–1844) was an early investigator of the internal structure of fossil plants. He was a fellow of the Geological Society of London and of the Royal and Wernerian Societies of Edinburgh.
Born Henry Silvertop, he married Eliza, daughter of Thomas Witham, esq. of Headlam, in the county of Durham, and niece and heiress of William Witham, esq. of Cliffe, in Richmondshire, North Yorkshire, and thus inherited the Witham name and Coat of arms.
Though having no botanical training, he applied William Nicol's method of examining fossils and rocks under the microscope by slicing them into thin sections. Nicol's first published account of this process is contained in Witham's 1831 publication, Observations of Fossil Vegetables. Witham's findings were also published in his 1833 book The Internal Structure of Fossil Vegetables found in the Carboniferous and Oolitic deposits of Great Britain, illustrated by William MacGillivray.
- "Mr. Watham's Observations of Fossil Vegetables" Sir David Brewster, The Edinburgh Journal of Science (1831) Vol.8, p.183
- John Burke (1836). A genealogical and heraldic history of the commoners of Great Britain and Ireland.
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- Observations on Fossil Vegetables, Accompanied by Representations of Their Internal Structure as Seen Through the Microscope (1831)