Mozart also gave lessons in the theory of music, sometimes even to ladies; we hear of a cousin of the Abbé Stadler as Mozart's pupil in thorough-bass. The exercise-book which he used for instruction in thorough-bass in 1784 is now in the Imperial library at Vienna.[36] Mozart wrote down a very characteristic melody, or a bass, or both, which the pupil was to arrange in several parts; then Mozart corrected the passage with short remarks on the various mistakes, alternately Italian or German, sometimes of a comic nature--for instance: "Ho l' onore di dirla, che lei ha fatta la scioc-cagine (da par Suo) di far due ottave tra il 2do Violino ed il Basso"; or in German: "This E is very forced here; it shows that it has only been put in to prevent too rapid a passage from one consonance to another--just as bad poets often do stupid things for the sake of rhyme. You might have gone gradually from C to D very prettily by inserting thirds." These remarks are purely grammatical; and it is evident that Mozart's teaching was of the good old-fashioned kind, which strives first to give the pupil a thorough knowledge of the grammar of his art. From exercise-books of this kind, of which Zelter saw one in Vienna,[37] a little {MARRIED LIFE.} (282) handbook of thorough-bass was afterwards printed under Mozart's name, and was much in use for some time.[38] With more advanced pupils he naturally proceeded differently. Attwood preserved an exercise-book with compositions, which he had submitted to Mozart shortly after his arrival in Vienna. Mozart had crossed out whole passages, and rewritten them with the remark, "I should have done this so."[39] When Kelly, the tenor, who made pretty little songs which Mozart admired, imagined that he could make himself into a serious composer by means of studies in counterpoint, Mozart said to him, "If you had studied counterpoint long ago in Naples, you would have done well; now that you have to give your mind to your education as a singer, you will make nothing of it. Remember that half-knowledge is a dangerous thing. You have considerable talent in the invention of melodies; a smattering of theory would ruin that, and you can always find some musician who can help you when you want it. Melody is the essence of music. I should compare one who invents melodies to a noble racehorse, and a mere contrapuntist to a hired post hack. So let it alone; and remember the old Italian proverb 'Chi sa più, meno sa.'"[40] Lesson-giving might fail greatly to increase either Mozart's fame or his income, but his success as a virtuoso was brilliant and lasting. His father warned him, when he talked of settling in Vienna, of the fickleness of the public, but Wolfgang answered cheerfully (June 2, 1781):--