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A hidden gem in the Royal Society Library is a treatise on petrified wood by (1577-1652).

Looking for resources to digitise for our , I was drawn to Stelluti’s (‘Treatise of the newly discovered fossil mineral wood’), published in Rome in 1637, because of the close-up illustrations of wood veining or ‘wave patterns’. Stelluti included 16 of these figures to show not only the variety of the waves and how they differ from conventional wood markings but also their beauty, as striking example of art forms in nature.

Wave patterns in fossilised wood: plate 5 of Stelluti’s Trattato ()

The investigation into the fossil wood of Umbria, Italy, was initially the work of , founder and patron of the . Stelluti, also a founder member, continued the project after Cesi’s death in 1630, and published their findings seven years later. He argued that the subterranean wood was a ‘metallophyte’, a type of hybrid between wood and metal, though much closer to plants in nature. In the illustrations below, plate 9 (left) shows small pieces of metal within a specimen, represented as small circles; a further example in plate 10 (right), labelled ‘A’, shows a piece of spice wood with ‘rods’ of metal running through its length.

Fossilised wood with metal: plates 9 and 10 of Stelluti’s Trattato ( and )

The Accademia dei Lincei (Academy of the Lynxes) is considered the world’s first scientific academy. A figure of their symbolic lynx can be seen on the title page of Stelluti’s treatise, representing the keen eyesight needed to discover truth through observation. This new philosophy of the early scientific academy brings to mind the Society’s motto Nullius in verba: take nobody’s word for it, and verify truth through an appeal to facts determined by experiment.

Detail from the title page of Stelluti’s Trattato

Debates into the nature of fossilised material were prominent in the seventeenth century. Stelluti’s book found its way to the Royal Society via the writer and alchemist , who had translated a copy given to him by and read his translation at a :

‘Mr Henshaw read the History of Lignum [wood] fossils minerale, as he had translated it out of a treatise written in Italian on the subject by Francesco Stelluti. He had the thanks of the Company and his paper was ordered to be laid up, together with the printed book presented by him to the Society from Sir Robert Paston, and committed to Dr Goddard’s custody.’

Henshaw’s translation survives in our Classified Papers series () and can now be read on our platform, although any mention of the aesthetic quality of the grain pattern seems to have been omitted.

The custodian of Stelluti’s work was , a Founder Fellow and Council member of the Royal Society. A physician by trade, Goddard was curious about wider natural philosophical subjects, and submitted papers to the Royal Society on and on the texture of wood. A states that ‘Mr Hook produced Dr Goddards petrifyed wood’ which he had observed under a microscope.

, in turn, published his observations of ‘Petrify’d wood, and other petrify’d bodies’ in his great 1665 work , looking at several specimens and drawing comparisons with rotten wood and charcoal. He concluded that the reason for the phenomenon was due to a process of wood being soaked in water ‘impregnated with stony and earthly particles’. These microscopical observations were significant in clarifying that petrified wood and other fossils had once been living organisms.

A microscopical study showing the pores of charcoal and petrified wood: Schem. X from Hooke’s Micrographia ()

The original drawings of the ‘metallophyte’, done for Cesi and Stelluti, were bought by another Accademia dei Lincei member, , shortly after Cesi’s untimely death in 1630 and before the printing of the treatise. Dal Pozzo, along with his younger brother Carlo Antonio, amassed a large collection of drawings and prints over a broad range of subjects, capturing the human knowledge of the period in visual form. This great collection, known as the Museo Carteceo or and comprising over 10,000 artworks, was acquired by King George III in 1762 and now resides in the Royal Library at Windsor Castle.

Polished slice of petrified wood by Michael Gäbler, CC BY 3.0, via

The allure of petrified wood still holds today, with lapidary items fetching a high price. The art of transforming fossilised wood into furniture and objets d’art was also practised by Cesi, and a fossil wood tabletop from his collection was given by dal Pozzo to and shown at a . Although the tabletop does not survive in our archives today, its presence at the meeting is indicative of a thriving seventeenth-century research area. The treatise by Stelluti along with the original drawings, meanwhile, are an important – and beautiful – resource for the understanding of the state of mineralogical knowledge at the time.