John's College is second only to that at Trinity. It is approached by a staircase of singular beauty. At Magdalene is the Pepys Library; and the libraries of Peterhouse, Trinity Hall, and Queens' are good specimens of mediæval college collections. The University has two public libraries. Of these the University Library proper enjoys the right to a copy of every book printed in the realm. It numbers some 500,000 volumes, and is rich in every kind of literature. The rule which allows M.A.'s and certain B.A.'s to borrow books, and which gives readers access to the shelves, makes this library, as Lord Acton said, "the only useful library in Europe". The library of the Fitzwilliam Museum includes a remarkable collection of musical manuscripts, the most valuable of which are manuscripts of Bach, Handel, and Beethoven. During the last hundred years Cambridge has been enriched with numerous laboratories and several collegiate institutions. Of the latter the most important is Downing College, built in 1805. Two professors have their maintenance here: one of Medicine, the other of the Laws of England. On Downing property the present Law Schools, Geological Museum, and other of the more recent habitations of science have been built. The great Cavendish Laboratory, to which the seventh Duke of Devonshire was a conspicuous benefactor, was built in 1874. Almost every branch of science now possesses its special museum, while art and the study of antiquities are served by the Fitzwilliam and the Archæological Museums. Cambridge to-day is a large and complex community: the undergraduate population alone has reached nearly four thousand souls. The Senate, or body of M.A.'s having voting powers in the government of the University, numbers over seven thousand persons; while the total number of members of the University who still keep their names "on the boards" stands at 14,758. Every kind of study, from astral chemistry to engineering, finds among this mass of people some professed teachers and eager students.