sentences:  Steadily enriched by a sequence of outstanding gifts over several centuries, even the French Revolution and the Napoleonic Era did little lasting harm.By the end of the 19th century the library encompassed close to half a million books, and tens of thousands of manuscripts.Several of the Popes (Leo XIII and Pius XI) have taken a keen and active interest in the library, and great effort and expense has been taken to ensure that the collections not only continue to grow but are well cared-for.