Whenever science historian John van Wyhe passed through the old library of Christ's College at Cambridge University, he took a moment to glance at a photo of Charles Darwin hanging on the wall. "I've always been curious about it, because in the frame there's a signature on a bit of paper, and it looks like there's something written on the back."

Darwin's old cheque was folded up and stuck in a picture frame to show off his signature, which was written on the back. This small square, exposed to the light from 1909 onwards, is now a different colour.http://darwin-online.org.uk/

When van Wyhe finally got around to investigating the matter, he was met with a pleasant surprise. The signature is actually on the back of a cheque, folded and embedded into the frame back in 1909. The find makes for a very rare discovery — most of Darwin's papers were tracked down and catalogued long ago. "New things don't turn up anymore," says van Wyhe, who is director of a project hosting Darwin's complete works online at the University of Cambridge, UK.

The cheque could also be seen to tell a little about Darwin's character: "It's funny, because he signed the wrong side at first," says van Wyhe. Darwin's name has been scribbled out on the front of the cheque, presumably before he properly endorsed it with the signature on the back.

No one knows how or why this mistake was made. "He was very canny about money," notes Shelley Innes, with the Darwin Correspondence Project at University Library, Cambridge. "He was a treasurer for a society, and kept the school accounts too. One of his sons was a banker."

But van Wyhe notes that not all of Darwin's character was fastidious. "Darwin is very careful in his science. But there are some things he doesn't consider to be very important. He's always apologizing for his poor handwriting."

Money to go

The cheque is for £100, made out by Darwin "to self" to withdraw cash from his own account. "That's a lot," says van Wyhe.

The money was probably withdrawn simply for use in everyday expenses, speculates van Wyhe. Records show that Darwin was paid by his American publisher for an edition of The Descent of Man on 16 March 1872, when he and his family were staying at a rented holiday home in London. His diary shows that they left London on 21 March to go back to their home in the village of Downe, Kent — the same day the cheque was made out. It was probably Darwin's way of taking some cash from the big city back to the countryside.

Darwin never did like his serious expression in this photo.http://darwin-online.org.uk/

Darwin was also well-known for giving generous gifts, says Innes, so the cash could have been for some sort of donation.

Unfair likeness

The photo originates sometime in the mid 1850s (Darwin himself apparently didn't like it much, having once written of the photo: "If I really have as bad an expression as my photograph gives me, how I can have one single friend is surprising.") and was displayed during the Darwin centenary exhibition in 1909.

Darwin's son Francis was at that exhibition, so van Wyhe supposes that he may have handed over the cheque as a gift, in order to provide a signature to accompany the photo. "He probably had a whole stack of such papers," says van Wyhe. The snap, with signature incorporated into the frame, was then given to Christ's College in 1934.

The painting and cheque will now both be conserved according to modern standards, says van Wyhe. The cheque, which belongs to Christ's College, is presumably quite valuable, but no one has any immediate plans to sell it.

Books and letters signed by Charles Darwin are available for purchase on various internet trading sites for hundreds or thousands of dollars. "We have in the archive quite a few cheques by him. But I wouldn't be able to hazard a guess as to where in the market value Darwin cheques would be," says Innes. "Anything with his name on it has a certain cache."

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