Darwin's notebooks from the voyage of the H.M.S. Beagle are being placed online by the English Heritage society, which cares for Darwin's Down House. There is a problem, though, because one of Darwin's notebooks is missing and it is the Galapagos notebook. It is thought to have been taken from Down House sometime in the 1970s or 1980s. The BBC World Service story is here. The appeal from English Heritage can be read here.
Here is their description of the notebook.
Darwin used different types of notebooks and the missing Galapagos notebook is small, almost square, and bound in leather with a brass clasp. It is labelled on the outside with a rough itinerary in Darwin's handwriting, marked "Galapagos. Otaheite. Lima." It contains entries he made between March and November 1835 when he was in Chile, Peru, the Galapagos and Tahiti. Inside the front cover is written: "63.5 C. Darwin H.M. Beagle". About a third of the notes were written from the front with the rest starting again from the back of the book. Darwin usually crossed out each page when he had written up the contents, either in his diary or in one of his more formal notebooks. All the Beagle notebooks are mostly written in pencil.