Among forms that Chopin made his own was the Nocturne, at one time synonymous with the Serenade, but with the Irish pianist John Field and Chopin, his successor, a lyrical piano piece offering, nominally at least, a poetic vision of the night. Field wrote eighteen piano pieces with this title between the years 1814 and 1835 and these introduced a new form of piano music that was developed not only in the Nocturne but in other separate movements for piano throughout the century. Two nocturnes were published in 1840 by Eugéne-Thèodore Troupenas, who briefly replaced Schlesinger, whom Chopin now accused of sharp practice in disposing of one of his German copyrights, giving vent, in private correspondence, to his rooted anti-semiotic suspicions. The G minor Nocturne, Opus 37, No. 1, encloses a tranquil chordal E flat major section, and is followed by a G major Nocturne, with a lilting secondary episode. By 1841 disagreement with Schlesinger had been put aside and he published a set of two nocturnes, the first in C minor and the second in F sharp minor, dedicated to Chopin's pupil Laure Duperré. Opus 48, No.1, moves forward to a central C major section of gentler character, increasing in excitement as the opening material returns. The F sharp minor Nocturne that completes the set moves into a relatively sombre D flat major section of some harmonic complexity. Two more nocturnes were published by Schlesinger in 1844, dedicated to Jane Stirling, a middle-aged Scottish pupil of Chopin whose nuptial ambitions outweighed her musical talent. It was through her that Chopin travelled in 1848 to London and to Scotland and to an endless round of tedious social visits that lasted seven months, until he could escape back to Paris again, his health now much worse. In 1844, however, Chopin was still involved with George Sand, although their relationship had it's difficulties as her two children, Maurice and Solange, grew up and used him in their own rivalries and jealousies. The F minor Nocturne, Opus 55, No. 1, allows the opening material to re-appear in more elaborate form in conclusion. It is followed by a second, the Nocturne in E flat, marked by it's use of a second melodic voice, accompanying the first. Chopin wrote his last two nocturnes in 1846 and they were published in the same year by Brandus, who had bought Maurice Schlesinger's business and was later to acquire Troupenas. They were dedicated to another of the composer's piano pupils, Mlle. de Kînneritz. Opus 62, No.1, in B major, is introduced by two chords, the first suggesting another tonality. There is an A flat major central section and an elaborated return of the material of the opening section. The final work, the Nocturne in E major, has a secondary episode with a more energetic accompanying figure. The two nocturnes were written in the autumn of 1846 at Nohant, which Chopin only left in November to return alone to Paris, giving rise to rumors about a quarrel with George Sand, with whom he quarreled definitively the following year, after her daughter's marriage.