Stones, Sharks and Steno’s De Solido

Written by Ted Simonds, Graduate Trainee Library Assistant.

Today is #OldRockDay, a day to celebrate all things old, rocky, and fossilised. The library of Herbert Leader Hawkins (1887 – 1968), professor of geology at the University of Reading, forms our Hawkins Collection, which contains rare books on the history of geology, palaeontology and echinoderms. There are few works more important or rare in the field than Nicolaus Steno’s De solido. Written in the late 1660s, and printed in 1669, the work is the first to put forward the theory that the earth is made up of strata – or, layered rocks – and the principals that underly this. Not to be seen as a single polished work, De solido is an unfinished introduction to a thesis grown out of a lifetime’s worth of investigations in anatomy.

Title page of Steno’s ‘De Solido’

Nicolaus Steno (1638-1686) saw his life’s work as a series of unfinished investigations. The Danish scientist studied medicine in Copenhagen before moving to Amsterdam, Leiden, Paris, and Montpellier, before arriving in Italy in 1666. It was whilst in Florence that the De Solido was printed in 1669.

Over a life-time of enquiry, Steno had started investigations aiming to uncover all the glands of the human body, probing the structure of the heart, muscle tissue, and conducted other investigations into the construction of egg shells, the bodies of fish; hot springs, tobacco powder, and the coldness and dampness of caves. Most of these investigations were called off early, or never amounted to the breakthrough he anticipated. In De Solido, Steno looks back over his scientific accomplishments and writes:

new tasks have always stood in the way of the completion of initial undertakings

His study of glands was called off when he decided to consider the heart’s structure, and that investigation was halted by the deaths of his stepfather and mother in October 1663 and June 1664, when he was living in France. Steno started De Solido as a diversion from his ongoing work on muscles. By the end of 1666 he was in Italy, where his book Mycology was ready to be edited and promised to be an important work on the study and structure of muscles.

However, as always, a new diversion lay just around the corner; in the autumn of that year French fishermen off the coast of Tuscany caught an enormous shark. The  of the shark was recorded in a letter, written from the philosopher Lorenzo Magalotti to the Archbishop of Siena, Ascanio II Piccolomini, dated October 26th, 1666. The philosopher tells the Archbishop how:

between Gorgona and Meloria, some miles off from Livorno, a French fishing boat had observed over the water the head of a shark

The letter offers a grizzly account of how the shark was hauled out of the water with a sling, tied to a tree on land, and bludgeoned to death. The letter relates how the liver alone weighed 300 lb, the rest of the organs 2400 lb, and the fish as a whole was estimated to weight 3500 lb. How could such a seemingly tangential event derail Steno’s study of muscles? And what relevance does this bear on the history of geology?

The head of the shark that had initially caught the fishermen’s eyes became big news – and the cadaver was transported to Florence and presented to Steno. Steno had dissected a ray the year before, and given his expertise in anatomy it followed that he was the person  best qualified to dissect such an especially large shark. The dissection was a public event attended by many, and the findings were written up in 1667. Much like his dissection of a ray in 1666, the written report is anatomical in structure, but unlike the previous dissection, has wider-reaching implications than just the body of the shark.

Steno reused Gerard Blasius’ image of a shark’s head to illustrate his dissection. Seen here in the Cole Papers (MS 5315/4/2/23)

The report printed in 1667, Canis carchariae dissectum caput, glistens with detail. The description of the shark is granular. As one reads, one is told of the different kinds of touches and pressures Steno performed upon the creature; the effects of blowing upon certain parts of the body; the textures, smells and colours of the fish. Structured anatomically, Steno moves through skin, cartilage, bone; the eyes, nerves and jaws of the shark. After which Steno describes the teeth.

When Steno observed the teeth of the shark, he made a leap only made by few people before him. Glossopetrae (or ‘tongue stones’) are triangular shaped stones believed by Pliny the Elder to have fallen form outer space, and by later thinkers to have been the tongues of serpents, turned to stone by St Paul. Fabio Colonna, in his 1620 dissertation De glossopetris dissertatio, was the first scientist to argue that these stones were the teeth of sharks. In adjacent circles across Europe, John Ray, Martin Lister, and Robert Hooke were thinking along similar lines. Nonetheless, in Steno’s writing one observes something like an illumination.

In Canis carchariae, Steno begins a new chapter to think this through: ‘Digression on Bodies Resembling Parts of Animals that Are Dug from the Earth’. He raises a series of questions; has the land always had the same firmness? Was the earth once covered with water? Was soil once sediment? All circling around a central question: how could one body come to be enclosed within another body? A shark’s tooth enclosed within the earth?

Steno concludes that “those who assert that large tongue stones are the teeth of a shark are not far from the truth”. Steno’s predecessors and peers had not made this link quite as explicitly, and where they had, had not gone far enough in asking how.

Steno believed his eyes when he saw the shark’s teeth and recognised the glossopetrae he had seen before in Ole Worm’s museum in Denmark as a youth (Steno was friends with Worm’s son, Willum), or those shown to him by his teacher Thomas Bartholin, or friend Ole Borch. Interestingly, his student notes of the 1640s record a curiosity in the matter:

“Snails, shells, oysters, fish, etc., found petrified on places far remote from the sea. Either they have remained there after an ancient flood or because the bed of the seas has slowly been changed. On the change of the surface of the earth I plan a book, etc.”

It would seem that the questions Steno had been asking; the half-finished projects, and the new investigations he had begun had all been orbiting around a central theme. What connects muscle fibres, the glands of the body, the human heart, chicks within eggs, fossils, and caves in the ground? Taking a step back, Steno asked the question: how can a solid come to be naturally contained within another solid? This question gives us the full title of Steno’s De Solido, which is De solido intra solidum naturaliter content dissertationis, or “Dissertation on a solid naturally contained within a solid”.

Printed in 1669 as an introduction to what Steno promised to be a longer work, De solido (also called the Prodomus) puts forward – for the first time – the notion that “the strata of the earth’s crust contain the records of a chronological sequence of events from which the history of the earth can be reconstructed”. (Printing & the Mind of Man, 151).

Illustrated plate from De Solido demonstrating the strata of the earth, and how things come to be encased within them.

The work is celebrated as the first work of modern geology, crystallography, and stratigraphy. As easy as it is to laud Steno’s work for its originality and clarity of vision, it is easy to forget that it also operates as an apology. Steno’s time in Florence – under patronage of Grand Duke Ferdinand II – was coming to a close as pressure mounted on Steno to return to Denmark. De solido opens humbly. He reflects on his sporadic working life, and addresses his patron to apologise:

since I am not able to complete all that was to be shown to you, I shall show you the chief items of what has been completed, so that I may not seem to have broken my word

Steno’s reluctance to break his word is not consistent with his actions in breaking the world into laminate strata. Whether known to him or not, his work stands at odds with early modern religious beliefs in the age of the world and the nature of God’s creation of it. There is a subtle irony in the end matter of the book. Rather than a continuation of his work, the final pages of De solido contain testimonies from church authorities that validate that nothing in the book contradicts the word of God. Like the facts of his life, after the production of De Solido, Steno turned to the church and died in poverty in Schwein in 1686.

Appendix showing religious authorisation of the text.

De Solido tries to make sense of how it could be that something as old as the earth itself, could contain within it things that are older. Even if Steno never found an answer to his question, it was important that he asked the question. And if Steno saw his life as a series of incomplete undertakings, we can appreciate an overarching aspiration to think deeply and protactedly about the nature of the earth, and more than that, puzzled at how we can think beyond the surface of our limitations.

Printer’s decoration on the title page of ‘De solido’. Showing the Medici rosebush.

Steno in the Special Collections

Steno, De solido. 1668. [HAWKINS COLLECTION—STE]

Steno, The prodromus to a dissertation. 1671. [COLE–398/04]

Steno, Elementorum myologiae specimen. 1669. [COLE–398/03]

Steno, De musculis et glandulis. 1664. [COLE–398/06]

Troels Kardel, Steno : life, science, philosophy. (Copenhagen : Danish National Library of Science and Medicine, 1994.) [COLE–398]

MS 5315/4/2/23. Glass negative. Images of pages from a book or books by Gerard Blasius. Including the image of a shark’s head. Steno republished this image in his 1667 Canis carchariae dissectum caput.

MS 5315/4/2/130. Glass negative. Images of pages from a book or books by Jaccobsen and Steno. Includes image of the gut of a heron from vol. II of ‘Acta Medica Hafniensis’.

MS 5315/4/2/248. Glass negative. Images of pages from a book or books by Steno. Includes the title page from ‘Myologiae Specimen, seu Musculi Descriptio Geometric’. Includes a portrait of Steno. Includes figures from ‘Acta Medica Hafniensis’ vol II.

We also hold 17th century books by Steno’s contemporaries; Thomas Bartholin (1616-1680), Gerardus Leonardus Blasius (1626?-1692),

Steno Online

Digital facsimile of Steno’s De Solido held at the Dibner Library of the History of Science and Technology, Smithsonian Institution Libraries:

Works consulted and further reading

Kardel, Troels, Maquet, Paul, Nicolaus Steno: Biography and Original Papers of a 17th Century Scientist. Second edition. Springer, 2013.

This volume brings together an in depth biography of Steno, and publishes (English) translations of his major printed works, containing reference to manuscript items. There is a lengthy bibliography.

Cutler, A. The Seashell on the Mountaintop: A Story of Science, Sainthood, and the Humble Genius who Discovered a New History of the Earth. Dutton, 2003.

Dall’Aglio, S. ‘The great collector and his man in Rome: Leopoldo de’ Medici and his letters to Ottavio Falconieri, 1662-75’. Journal of The History of Collections. 2019.

Moran, M.E. Urolithiasis: A Comprehensive History. Springer, 2014.

The Pitt Rivers Museum, ‘Tongue Stone, France’, in Small Blessings: Amulets at the Pitt Rivers Museum. 2012. Web: [Accessed July 2020].

Yamada, Toshihiro, ‘Hooke–Steno relations reconsidered: Reassessing the roles of Ole Borch and Robert Boyle’. In Gary D. Rosenberg (ed.) The Revolution in Geology from the Renaissance to the Enlightenment. Geological Society of America, Memoir 208. 2009. Web: [Accessed July 2020].

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