It is likely that Ruskin did not encounter the Liber Studiorum before 1843, for the first edition of Modern Painters I contains no mention of it (all the references to the Liber were added to the third edition (1846)). This is surprising, because Ruskin had been taking drawing lessons with J. D. Harding intermittently since 1840, and Harding generally encouraged his pupils to study the Liber. In fact Ruskin's first recorded references to it occur many months after the publication of Modern Painters I, in a letter to W. L. Brown in November 1843 ( Works, 36.33) where, significantly, his discussion concerns the unity of the Liber Studiorum. Ruskin found it impossible to acquire a full set of the Liber until 1845; see Ruskin as a collector of the Liber Studiorum.