Johnson's notes to the plays of Shakespeare are an invaluable source of information of many kinds. I can only suggest here, and give a few examples of, the wealth of material that awaits further, detailed examination by other scholars. One demonstration, however, of the use to which the notes can be put is provided by Professor E. L. McAdam's _Dr. Johnson and the English Law_ (1951) in which are recorded notes showing Johnson's familiarity with various legal terms. Further insight into Johnson's knowledge of books of _esoterica_, histories, ballads, etc., can be gleaned from the comments on Shakespeare. A subject in which I must confess an interest possibly out of proportion to its worth is that of Johnson's reading. Some day we will have a list, probably never complete, of the books we can be sure Johnson knew. Not only will the notes to Shakespeare supply the names of works that Johnson knew, quoted from, or alluded to only in these notes, but they will also help to establish more firmly certain fields or subjects that fascinated him. Thus, one note is evidence for Johnson's knowledge of Guevara's _Dial of Princes_; another for his familiarity with Ficino's _De Vita Libri Tres_; and nowhere else in Johnson's works, letters, or conversation are these works so much as alluded, to. Other notes show us that Johnson remembered now a poem, now an essay, from the _Gentleman's Magazine_. In still other notes one encounters or is able to identify the names of John Caius, John Trevisa, Dr. William Alabaster, Paul Scarron, Abraham Ortelius, Meric Casaubon, and many others. Plays, sermons, travel books, ballads, romances, proverbs, poems, histories, biographies, essays, letters, documents--all have their place in the notes to Shakespeare. No discussion of Johnson's knowledge of books can ignore the importance of his reading for the _Dictionary_. Nor can this same preparatory reading be overlooked in a consideration of the Shakespeare edition. Between one-fifth and one-fourth of the notes to Shakespeare can be traced back to the _Dictionary_. What is more, the revision of the 1765 _Shakespeare_ was undertaken at the same time that Johnson was revising his _Dictionary_; both revisions appeared in the same year. And so one is not surprised to find that these two labors are of reciprocal assistance. One illustration will have to do duty for several: in a note Johnson observes of the verb "to roam" that it is "supposed to be derived from the cant of vagabonds, who often pretended a pilgrimage to Rome;" this etymology is absent from the 1755 _Dictionary_; in the revised _Dictionary_ the verb "is imagined to come from the pretenses of vagrants, who always said they were going to Rome." A number of the new notes and comments in the 1773 Shakespeare are clearly derived, directly or indirectly, from the _Dictionary_.