Astronomers have to keep up to date about what is done elsewhere. For this, they must read specialized books and articles. The articles are in general available over the Internet, but this service is not free and is organized by the Observatory library. It is increasingly rare to see scientists in a library reading room consulting books or historians searching ancient documents. This does not mean that the importance of the library has diminished, rather its purpose is now to conserve and exploit the very rich collection of documents and historical instruments of the Observatory.
