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Darwin Correspondence Project

Epsilon: building a collaborative digital framework for c19 letters of science

Arago to Young pc sized.jpg

Letter from François Arago to Thomas Young
Courtesy of the Royal Society

ƐPSILON is both a research consortium and a developing, flexible, technical infrastructure for recreating the network of practitioners who expanded scientific knowledge in the long nineteenth century. It promotes and supports the digital creation, delivery, and preservation of scientific correspondence. Designed to link letter-texts from multiple sources for cross-searching and analysis, Epsilon opens up c19th science letters to the next generation of researchers and to the widest possible public audience.

Its founding partners are:

Together with Cambridge Digital Library,The Royal Institution, and The Royal Society of London

A beta version of the site was demonstrated at the History of Science Society meeting in Toronto in November 2017. The first public version ( launched at the joint meeting of the British and European History of Science Societies in September 2018 (speakers and abstracts for the conference session are here).

ƐPSILON is designed to:

  • Maintain the independent identity of ongoing projects
  • Recognise the right of the originator to be identified
  • Accept material in multiple formats
  • Offer different levels of controlled access

And to take texts, metadata, and images from:

  • Completed and ongoing born-digital projects
  • Orphaned digital projects
  • Print only projects, completed, in progress, in and out of copyright
  • Print and digital projects in various formats
  • Ebook publications
  • Individual digital transcriptions of letters created by scholars
  • Crowd-sourced transcription from digitised images

How? We map letter data to TEI P5 XML encoding using the <correspDesc> metadata exchange element set. Advice on conversion and on using XML as an editing format is available.   Search is powered by XTF, an open source tool.

ƐPSILON Rights Notice and Takedown policy


We are most grateful to the editors and publishers of the various collections represented on the Epsilon site ( for making metadata and letter texts available.  Those editions in turn would not be possible without the generous support of many copyright holders.  While the contributors of content to Epsilon are responsible for ensuring compliance with legislation, if you are a rights holder and are concerned that you have found material on the Epsilon website for which you have not given permission or which is not covered by a legal exception or exemption, in addition to contacting the contributor, please also contact us stating the following:


  • Your contact details
  • The full bibliographical details of the material
  • The exact and full URL where you found the material
  • A statement and any proof you may provide that you are the rights holder or are an authorised representative thereof.

Upon receipt of notification, the Epsilon team will acknowledge receipt of your complaint by email or letter and will make an initial assessment of the validity of the complaint.  Upon receipt of a valid complaint the material will be removed from the Epsilon website pending an agreed solution.

Contact us at:

Epsilon, c/o Darwin Correspondence Project
University Library
West Road

Email, with the subject line ‘Epsilon rights’ and providing the details as above, may be sent to


In this section:

ƐPSILON is now live at

Interested? We would like to hear from you.

If you have letters or ideas for ƐPSILON, please email us at

For information about how we handle your personal data, please see .

Why ƐPSILON? The fifth letter of the Greek alphabet is used as a variable in almost every branch of science.  Its range of meanings include ‘set membership’, ‘elasticity’, and an ‘arbitrarily small positive quantity’.  And it also stands for ‘Epistles of Science in the Long Nineteenth century’.

ƐPSILON is funded, via the Darwin Correspondence Project and Cambridge University Library, as a publicly accessible platform, and as a repository for accepted TEI XML encoded data.

Have letters? Have ideas? Please join us.