 Sometime before 1542, Melzi gathered together the papers for "A Treatise on Painting" from 18 of Leonardo's 'books' (two-thirds of which have gone missing).After Melzi's death in 1570, the collection passed to his son, the lawyer Orazio, who initially took little interest in the journals, but they were later dispersed.A version of the treatise was published in France in 1632.