More than 500 manuscripts, first editions and letters from the Honresfield Library will be offered across three auctions, with the first to run online on July 2-13.
The collection was originally put together by Arthur Bell Nicholls, the widower of Charlotte Brontë, and later acquired by Rochdale mill owners Alfred and William Law who lived at Honresfield House – 20 miles from the Brontë family home in Haworth.
Following their deaths the library was inherited by a nephew, Sir Alfred Law, in 1913 and has since remained in the family.
The Brontë Society & Brontë Parsonage Museum fears the splitting of the library will be detrimental to the study of the literary family.
Ann Dinsdale, principal curator at the museum, said: “The society believes that the rightful home for these unique and extraordinary manuscripts, unseen for 100 years, is at the Brontë Parsonage Museum, where they can be enjoyed by visitors, explored by scholars and shared with Brontë enthusiasts for generations to come.”
Among the items in the library is a book of 29 handwritten poems by Emily with an estimate of £800,000-1.2m. It is the only surviving handwritten manuscript to feature some of her best-known verse, including No Coward Soul Is Mine, The Bluebell and The Old Stoic.
The Brontë family’s copy of Thomas Bewick’s A History of British Birds – as mentioned in Jane Eyre – is also part of the archive.
The museum hopes to fundraise to secure some of the lots. However, it is concerned it will not be able to have the time to put together financing and plan.
Dinsdale added: “We are determined to save as much as we can, but due to the dramatic financial impact of the pandemic, the timing is unfortunate.
“Museum revenue has fallen away to almost nothing and competition for public funds has become fiercer than ever. We are, however, issuing a lobbying call to action to do what we can.”