Roger Bacon's Optics

Roger Bacon's Optics

An inside look at books featured at the May 2024 Trimble Lecture
Books lying open on supports on a table.

Rare Book Display from the Niels Bohr Library & Archives at the May 8th, 2024 Trimble Lecture with Elly Truitt at the American Center for Physics (D.C.), featuring books by Roger Bacon.

On Wednesday, May 8th, 2024, the American Institute of Physics (AIP) had its first lecture of the 2024 Lyne Starling Trimble History of Science Public Event Series at our new American Center for Physics space in downtown Washington, D.C. Professor Elly Truitt of the University of Pennsylvania, gave the fascinating lecture, “A Thirteenth-Century Perspective on Optical Science and Experiment: The Case of Roger Bacon”.

For those of you who missed the lecture, it is available on the AIP History YouTube Channel until 5 PM EST on Monday May 20th, after which it will be made private until Elly Truitt’s forthcoming book Marvelous Inventions: Roger Bacon, the Middle Ages, and the Making of Modern Science becomes available (anticipated next year).

Before the talk, representatives of the Niels Bohr Library & Archives (NBLA) hosted a book display with two volumes by Roger Bacon from our rare book collection related to Professor Truitt’s talk. In this blog post, we are going to give you a behind-the-scenes look at the unique, centuries-old books featured at the lecture!

Librarian showing books on a display table to Professor Truitt
Niels Bohr Library & Archives Librarian, Karina Cooper, shows speaker Professor Elly Truitt a 1750 edition of Roger Bacon's Opus Majus. Photo credit: Will Thomas.

Audience gathered around table with books
Professor Truitt gives a special presentation on the books from the Niels Bohr Library & Archives to the crowd before the lecture. Photo credit: Will Thomas.

The books featured were versions of 13th-century philosopher and scientist Roger Bacon’s seminal work Opus Majus, originally written in 1267 for Pope Clement the IV but not published in print until centuries later. NBLA has a 1750 second edition of the first printed edition of the Opus Majus and a 1614 first printed edition of the fifth part of the Opus Majus on optics called Perspectiva

Opus Majus

Opus majus ad Clementem IV. pontificem maximum. Primum a Samuele Jebb M.D. Londini editum MDCCXXXIII. Nunc vero diligenter recusum. Accedit prologus galeatus in reliqua opera ejusdem autoris. By Roger Bacon (1214?-1294). Venetiis, Apud Franciscum Pitteri, MDCCL [1750]. NBL Call Number: WE-20180168


Opus Majus (Latin for “Greater Work”) was Roger Bacon’s first and arguably most significant work on the natural sciences, scientific method, and empiricism. A wide ranging treatise covering such topics as epistemology, theology, linguistics and grammar, to mathematics, optics, and experimental science (including alchemy and magic), it was commissioned by Pope Clement the IV in 1267 to explain the nature of Bacon’s scholarly research for the Franciscan Order of the Catholic Church. The work was preserved in various medieval manuscripts and smaller sections of it were often published and circulated separately. It was not fully published in print until 1733, when English physician and scholar Samuel Jebb published his edition of Opus Majus, based on a manuscript held at Trinity College, Cambridge. This edition of the Opus Majus was later republished in 1750 in Venice by Francesco Pitteri and continued to be the definitive edition of the work until the mid-19th century, when scholars realized it was incomplete. In reexamining Bacon’s manuscripts and later work Opus Tertium, scholars discovered that Jebb had actually left out the pinnacle final seventh part of the work: a treatise on moral philosophy, connecting science and other topics together with religion. (For more on how they discovered Jebb’s edition was incomplete, see this contemporary account by John Kells Ingram On the Opus Majus of Roger Bacon from 1858). It took several more decades, and consultation of several manuscripts, before a true complete edition of the Opus Majus was put into print by editor John Henry Bridges in 1897.

Here at the Niels Bohr Library and Archives, we have a copy of the 1750 reprint of Jebb’s edition of Opus Majus: Opus majus ad Clementem IV. pontificem maximum. Primum a Samuele Jebb M.D. Londini editum MDCCXXXIII. Nunc vero diligenter recusum. Accedit prologus galeatus in reliqua opera ejusdem autoris. (Latin for “The Greater Work [of Roger Bacon, Brother of the Order Minor], to Clement IV, Pope. First published in London 1733 by Samuel Jebb, M.D. Now accurately and faithfully reprinted. Includes a 'helmeted prologue' on the other works of the same author”). The book was acquired in 2018 as part of a collection of rare books on the history of science (for more on the collection, see this Ex Libris Universum series). 

Let’s take a closer look at our copy to see some of the cool features of this edition!

Cover of the NBLA 1750 edition of Opus Majus

Above you can see the cover of our copy; it is bound with leather and is a quarto size, meaning that the pages of the book were formed by folding sheets of printing paper into fourths. Quarto sized books are decently large and were designed for reading and studying rather than portability. While the binding of the book is not contemporary (likely rebound by an owner in the 19th or 20th century), the inside title page gives us a sense of our copy’s history, also called provenance. Below, on the bottom left of the title page you will see two stamps with religious symbols. These are library stamps from two different Franciscan Order libraries in Poland and Central Europe who owned this book at some point in the last 300 years, before it passed into the possession of booksellers, contemporary owners, and eventually us at Niels Bohr Library. Since Roger Bacon himself was part of the Franciscan Order of Friars Minor in the 13th century, it is particularly fascinating that our copy spent much of its life centuries later being used by fellow members and scholars of his faith. It is also fun to think about how far this book has traveled in its lifetime, from Venice to Poland to Florida to Maryland, and those are just the places we know of!

Title Page of our 1750 edition of Bacon’s Opus Majus. In the bottom left corner you can see the two library stamps. Top Stamp: O.F.M. in Silesia (Order of Friars Minor), Sigil. Bibl. Pro Studius; Bottom Stamp: Bibl. F.F. Min. Conv. (Book owned by a library of a Franciscan Order in Central Europe.)

Another fun thing to note about this edition is the presence of some decorative typographical elements. On the title page there is a vignette, or an engraved emblematic image, depicting cherubs in a garden tending a bush. Vignettes were sometimes used in books of this era to invoke the subject or purpose of the book through allegory. The edition also has “floriated initials”, or decorative capitals at the beginnings of chapters which often feature luscious natural landscapes such as trees and meadows.

Engraved illustration of two winged cherubs tending a potted shrub

Title Vignette in the 1750 edition of Opus Majus.

Floriated initial in the 1750 edition of Opus Majus.

However, despite the ornate decorative aspects interwoven with the text at the start of the book, the scientific figures and illustrations for the Opus Majus do not actually occur in line with the text. Instead, they were printed separately as a large foldout chart often included at either the front or back of the book. This was a common practice in that era, since the printing of figures was done using a different illustration method (engraving) than the decorative elements (which used the older woodcut method). Engraving required a special type of printing press that was not compatible with the movable type printing press, so the figures would be printed on a separate sheet that would be inserted into the book after it was printed. Our copy is unfortunately missing the three pull-out charts of figures meant to be in this edition, so to remedy this, a previous owner took photographs of a different edition that did include the figures as pullouts, and included prints of those pictures with our copy. 

Printed photographs of the figures meant to be folded charts in the 1750 edition of the Opus Majus included in the copy held at the Niels Bohr Library & Archives. 

Perspectiva and De Speculis Comburentibus

Perspectiua : in qua, quae ab aliis fuse traduntur, succincte, neruose & ita pertractantur, vt omnium intellectui facile pateant. By Roger Bacon (1214?-1294). Francofurti : Typis Wolffgangi Richteri, sumptibus Antonij Hummij, 1614. NBL Call Number: (Z) N8 BAC


Now, on to the Perspectiva! As mentioned earlier, although the complete work of the Opus Majus did not come into print until much later, individual sections of the work were printed separately and gained popularity in these small portable editions, sometimes mixed with other texts. The Niels Bohr Library and Archives has an example of such a book, printed in Germany in 1614, over a century before Jebb’s edition! This book contains the fifth part of Roger Bacon’s Opus Majus, known as Perspectiva (Latin for “Optics”), and is illustrated with figures throughout. The book also contains an additional work attributed to Roger Bacon, known as De Speculis Comburentibus (Latin for “On Burning Mirrors”) which delves into refraction and the use of mirrors to focus and amplify light. The book was purchased by the Niels Bohr Library & Archives in 2021 with the help of the Avenir Foundation (see our blog post about it). 

Title page of the 1614 first edition of the fifth book of Bacon’s Opus Majus. It also contains another treatise by Bacon not from the Opus Majus, but also sent to the Pope in 1267-68, on burning mirrors, De speculis comburentibus.

Above you can see the title page of the Pespectiva, which was printed in Frankfurt, Germany, in 1614. It was edited by Johannes Combach, a professor of philosophy and theology at the University of Marburg, and represents the first time Bacon’s treatise on optics from the Opus Majus was published in print (nunc primum in lucem editum). From the title page we can also see that book was type set (typis) by Wolfgang Richter and published (sumptibus) by Antonius Hummius. It is also worth noting that the title of the work, Perspectiua : in qua, quae ab aliis fuse traduntur, succincte, neruose & ita pertractantur, vt omnium intellectui facile pateant (Latin for “Optics: in which, that which has been handed down by others at length, is examined succinctly, carefully, and accurately, so that all these things are easily understood”) only refers to the treatise from the Opus Majus, even though this edition also includes the separate work De Speculis Comburentibus by Roger Bacon on burning mirrors.

Unlike the 1750 edition of the Opus Majus, this 1614 edition includes woodcut illustrations inline with the text.

The scientific diagrams in this edition were produced by the woodcut method, which meant that the images and labels were carved into a wood block based on hand drawn illustrations found in medieval manuscripts. Printers responsible for the setting the metal type for the text would leave space in the page layout for these blocks to be added, so that image and text could be printed together. Above is a figure from the fourth chapter of the book on optics, which describes the properties of the elements of the eye (e.g. cornea, white of the eye [albuginea] and the uvea), drawing heavily on the works of Islamic scholar Ḥasan Ibn al-Haytham (Alhazen) that had been translated into Latin in the 12th century. The Opus Majus as a whole drew on several Ancient Greek, Arabic, and Hebrew sources and texts on science which had only recently been introduced to the Western Europeans.

Our copy of this edition however has some extra special features and annotations that make it unique!

Marbled cover of the Niels Bohr Library's copy of the 1614 edition of Bacon's Perspectiva.

First, the cover! While they say don’t judge a book by its cover, who wouldn’t want to read this beautiful volume if you saw it sitting on the shelf! This book is bound with leather and paper boards dyed using the marbling technique, which creates the colorful and vibrant pattern (learn about the marbling technique and see other examples from our collection in this blog post from 2019: “Magical Marbled Paper”). It is an example of a modern antique-style binding, common in the late 19th and early 20th century, so it is important to note that this cover is much newer than the text inside. It was presumably rebound by its owner at the time (a bookplate in the front identifies them as “J. A. Freilich”) to make the book more attractive in their personal library.

Our copy of this book is particularly fascinating because it has notes and annotations by previous owners, known as “marginalia.” While we don’t know who or when these previous owners were in possession of this volume, we know that at least two people owned and used this book before it was rebound, since their handwritten notes in the margins remain. Interestingly, the engagement with text for both of these readers was only with the second work in the volume, De Speculis Comburentibus.

The first “scribal hand” wrote in pencil. They seemed mainly engaged with the text by highlighting important passages and occasionally writing a word or two in the margins. They liked to draw manicules, or little hands pointing a finger at interesting lines. If you have ever seen symbols like these in old-timey posters or books or the Wingdings font, ☛☞☜☚, they actually come from a tradition of readers drawing little cartoon hands in medieval manuscripts!

Here is an example of our pencil-wielding reader highlighting a passage:

penciled hand and annotations on the margin of a page

Marginalia in pencil in the left hand margin of a page in De Speculis Comburentibus

In the left hand margin you can see the reader using a variety of annotation methods including quotes “””, a manicule ☞ pointing to “apparebit”, and writing the slightly cut off “... de speculis” next to where it appears in the text. 

pencil drawing of a hand in a book margin

Another manicule ☜ pointing to an important passage next to an illustration.

The other reader, who used iron gall ink, likely came before our pencil scribe, which we can surmise through their use of Latin and older scribal abbreviations. They included a wide range of annotations and spelling corrections to both the text and images, particularly the set of full page illustrations at the back of the book. 

First, this reader notes at the top of the page that while this section is presented in the edition as Tractus de Speculis (A Treatise on Mirrors), it is also known by the title De Speculis Comburentibus.

Annotation to the title identifying that this section is Bacon's De Speculis Comburentibus.

Next we see the reader correcting the spelling of the word vmkefi in the text to “mukefi”, which occurs four times within this chapter. “Mukefi” is a Latin transliteration of the Arabic term for parabolic (مكافئ) which was misspelled as a result of a typographer's error. (This page also shows the pencil reader drawing another manicule!) 

Annotations by both scribal hands: Correction to "mukefi" and a manicule.

Lastly below, with these full page plates, we see the reader both annotating images directly and describing what they depict in Latin. The figures of interest depict how images are perceived by the eye (oculos

Annotated woodcut figures from the back of the 1614 edition of Perspectiva.

Being able to see how actual readers engaged and responded to these texts is one of my favorite things about working with special collections. You get the sense you are reading over someone else's shoulder and it helps bring the past to life. This book is not just the transmission of a text from the 1200s, but also a living, breathing work of history in its own right. It allows us a glimpse into the adventures it underwent – globetrotting, changing hands, and fascinating readers - until it reached us here at the Niels Bohr Library & Archives for the next chapter of its story. It is a reminder that we are stewards of these objects and just one stop on their centuries-long journey of existence.

We hope you enjoyed getting a glimpse at these gems from our collection. Be sure to check out Elly Truitt’s book Marvelous Inventions: Roger Bacon, the Middle Ages, and the Making of Modern Science when it comes out, and join us for the next Trimble Lecture on June 5th, 2024, with astrophysicists John Mather and Mark Clampin.


Perspectiva and De Speculis Comburentibus

Perspectiua : in qua, quae ab aliis fuse traduntur, succincte, neruose & ita pertractantur, vt omnium intellectui facile pateant. By Roger Bacon (1214?-1294). Francofurti : Typis Wolffgangi Richteri, sumptibus Antonij Hummij, 1614. NBL Call Number: (Z) N8 BAC

About the Author

Karina Cooper

Nancy Roman

Karina Cooper

Karina Cooper is a Librarian at the Niels Bohr Library & Archives. She holds a B.A. from Swarthmore College where she studied Classics and Astronomy and a Master’s in Library and Information Science from the University of Illinois Urbana-Champaign. Her work at NBLA mainly involves improving the accessibility, discoverability, and accuracy of the library’s collections and catalog. She also enjoys being able to combine her love of physics and ancient languages working with special collections at the Niels Bohr Library and being able to constantly learn new things. Outside of work, her hobbies include playing the violin, reading, and English and Scottish country dancing. One of her favorite books in the collection is The Glass Universe by Dava Sobel.

Caption: Nancy Roman shows Women in Astronomy Exhibit at the Smithsonian, Washington, DC circa 1974.

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