Notes and comments hand-written by Charles Darwin on the pages and margins of the books in his personal library are now available online for the first time, enabling new insights into the great naturalist’s thought processes and the development of the theory of evolution. The first phase of the project has just been completed, with 330 of the most heavily annotated books now accessible online at the Biodiversity Heritage Library.

Darwin’s scientific library comprised 1480 books, of which 730 contain abundant research notes in their margins. All the annotated books are in the process of being digitized, resulting in high-resolution images of each book’s pages showing Darwin’s handwriting along with a transcription of the notes in a companion panel.

Digitizing the volumes, the majority of which are held at Cambridge University Library, is a collaborative effort involving Cambridge, the Darwin Manuscripts Project at the American Museum of Natural History, the Natural History Museum, and the Biodiversity Heritage Library. It is supported jointly by the National Endowment for the Humanities (NEH) and the Joint Information Systems Committee in England.

Most of Darwin’s personal library rests at Cambridge University Library and at Down House, Darwin’s home in Kent. Although the majority of the books are scientific, some are humanities texts on subjects that Darwin transformed into scientific topics.

The page images can be manipulated and magnified, and the view can be adjusted to show a single page or two adjacent pages. Direct links are provided to related annotations, and the site enables users to search all the annotations in the books by word or phrase. The images of the annotations and the series of transcriptions accompanying each page allow everyone to see which passages Darwin found relevant to his work, stimulated his thinking, or just annoyed him as he read the work of others.

The project to record the online transcribed marginalia relies on the work of two scholars, Mario A. Di Gregorio and Nick Gill, published in the 1990s and now enhanced by Gill.