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Henry Pierrepont, Grace Pierrepont, and the Dorchester Library
Doctoral researcher and artist Catherine James explores the Dorchester family's role in the history of the RCP's library.
The Ghost in the Library
Among the treasures preserved in the RCP’s Dorchester Library you can find Evangelista Tartaglia’s Troublesome invention, which shows how to raise a sunk ship using nothing but rope, planks, and ballast. Nearby you can find the collected works of Archimedes, once owned by the renowned English mathematician John Dee. Sandwiched among the volumes is Galileo Galilei’s world-changing Dialogo.
Archimedes, Opera non nulla (Venice, 1558). Left: signature of John Dee. Right: annotations by the Marquis of Dorchester.
Scrolling through the library’s catalogue, you will also find books by Galileo’s followers Benedetto Castelli and Evangelista Torricelli, and a hefty volume by Galileo’s implacable opponent Giovanni Baptiste Riccioli.
But one prized book is nowhere to be found, even though Henry Pierrepont, Marquis of Dorchester, played a key role in seeing it into print.
That book was The mathematical collections and translations by Thomas Salusbury, which brought together writing by renowned authors from ancient Archimedes to contemporary powerhouses Galileo, Castelli, Torricelli, Pascal, and Descartes. Many of those sources can be found in the Dorchester Library today.
Galileo Galilei, Dialogo Massimi sistemi del mondo tolemaico e copernico (Florence, 1632)
Galileo’s Dialogo (Dialogue concerning the two chief world systems) shows that the revolving Earth orbits the unmoving Sun. This is the book that was banned by the Catholic Church and earned Galileo a life sentence under house arrest for ‘strong suspicion of heresy’.
The Dorchester Library holds a first edition of Galileo’s Dialogo, published in Italian. (It also holds a later edition published in Latin, the universal language of learning.)
The first, Italian, edition shows that even Galileo made mistakes. Three months after the Dialogo was published, Galileo noticed a maths error in it. Immediately, he sent a letter to his friend Benedetto Castelli in Rome, asking him to correct the mistake in all of the books that had been distributed there. In his letter, Galileo wrote:
In rereading it [my book] I came across an omitted printing error, which is on [page] 228, lines 12 and 13, where the numbers 72 and 100 [sic] should be corrected to 12 and 36.
Fortunately, Galileo got word to his translator, so the Latin edition appeared with the correction in place.
Interestingly, the RCP copy of the Italian Dialogo does not have the correction, indicating that it was not in Rome when Galileo wrote to Castelli asking for the mistake to be amended. Presumably the book had already travelled further afield.
Galileo’s method for investigating the physical world combined mathematics and experiment, the abstract and concrete. A literal-minded person coined a new term to describe the method: physico-mathematical-experimental method. (Hold that thought.)
Archimedes, Opera non nulla (Venice, 1558).
As Henry Pierrepont, Marquis of Dorchester strived to understand the mathematics that explained physical phenomena, he was not afraid to write in his books. Here again we see his scrawled notes in the copy of Archimedes previously owned by John Dee.
Evangelista Torricelli, De sphaera et solidis sphaeralibus (Florence, 1644)
Pierrepont was not the only person who wrote in his books. In De sphaera (On spheres) by Torricelli, the unknown reader noted a passage that relates to Archimedes’ De sphaera et cylindro (On spheres and cylinders), circa 225 BCE (upper left).
Evangelista Torricelli, De sphaera et solidis sphaeralibus (Florence, 1644)
Like all students, Pierrepont and other readers had to work hard to make sense of difficult concepts. They underlined, they wrote in the margins, they even worked out mathematical equations. Here a reader restates the geometrical explanation in algebraic form.
Nicolo Tartaglia, Inventione (Venice, 1606)
Alongside the hard maths, Thomas Salusbury’s Mathematical collections offered simple, practical projects. Nicolo Tartaglia’s invention for raising shipwrecks was especially useful for a nation that relied on merchant and naval vessels.
Drawing on Archimedes’ hydrostatics, Niccolo Tartaglia devised a clever solution:
Build a crane by joining two ships with heavy timbers and affixing ropes to the timbers. Lower the crane by loading the shops with heavy ballast until they ride very low in the water. Send divers to attach the ropes to the sunk ship.
Now dump the ballast. All rise!
Pierrepont’s personal librarian, Thomas Salusbury, spent years translating the books. Some he certainly found in Pierrepont’s collection. Others he borrowed from the legendary library of Pierrepont’s friend, Charles Scarburgh FRCP.
Salusbury probably had help from physicians and mathematicians who gathered in Pierrepont’s library to study and socialize. While the Mathematical Collections was at the printer, several of these friends who regularly met at Gresham College formed a club to promote the ‘physico-mathematical-experimental’ method.
They called it the Royal Society.
The Mathematical Collections was Salusbury’s most ambitious work, but another bears his personal touch.
Bibliotheca Marchionis Dorcestriae, 1664. MS2000/81
see moon, stars, geometric shapes, and instruments embedded in the ornamental H.
As librarian, Salusbury created a catalogue for Pierrepont’s library. His passion for books shines through in the attention he lavished on the handwriting, even trying his hand at illuminated letters.
Pierrepont not only employed Salusbury, he publicly endorsed the Mathematical collections. So why of all mathematical books, is that one not in the library now?
We do not know. Over the years the original may have been gifted, loaned, lost, damaged, or sold. Fewer than a dozen copies are known to exist today.
In place of the original, the RCP owns a limited-edition facsimile created through the unlikely partnership of renowned Galileo scholar Stillman Drake and bohemian rare-book dealer Jacob Zeitlin.
Mathematical collections and translations in two tomes by T.S., London, 1661 and 1665: in facsimile with an analytical and bio-bibliographical introduction by Stillman Drake (London, 1967)
Missing books are often called ghosts. The mystery of the Mathematical Collections haunts the Dorchester Library. In its place we see something more human: Pierrepont in his library as a patron and student of mathematics, joining with his friends to champion Galileo’s new science.
A note on provenance
Collectors may improve their libraries by rebinding or replacing old or damaged books with newer, cleaner or more valuable ones. The books in this display represent titles that were in Dorchester’s library in 1664, but we can’t be sure that the copies on display were in his library at that time. Some books may have been replaced, and several have been rebound.
Constance Hardesty, Mansfield College, University of Oxford
Constance Hardesty is author of ‘Thomas Salusbury’s Lesser Half: Mathematical Collections and Translations, Volume 1’, in Mathematical Book Histories:Printing, Provenance, and Practices of Reading (Birkhäuser, 2024).