Madame de Stael was always his friend, and in 1811 he went to her at Coppet, where by a happy chance he took up the study of botany, with August de Stael as instructor. Filled with enthusiasm for his new pursuit, he made excursions through Switzerland, collecting and botanizing. The period of indecision was at an end, and in 1812, at the age of thirty-one, he matriculated as student of medicine at the University of Berlin, and applied himself with resolution to the study of the natural sciences. During the war against Napoleon he sought refuge in Kunersdorf with the Itzenplitz family, where he occupied his time with botany and the instruction of young Itzenplitz. It was during this time (1813) that 'Peter Schlemihl's Wundersame Geschichte' (Peter Schlemihl's Wonderful History) was written,--one of the masterpieces of German literature. His 'Faust' and 'Fortunatus' had in some degree foreshadowed his later and more famous work,--'Faust' in the compact with the devil, 'Fortunatus' in the possession of the magical wishing-bag. The simple _motif_ of popular superstition, the loss of one's shadow, familiar in folk-stories and already developed by Goethe in his 'Tales,' and by Koerner in 'Der Teufel von Salamanca' (The Devil of Salamanca), was treated by Chamisso with admirable simplicity, directness of style, and realism of detail. Chamisso's divided allegiance to France and Germany made the political situation of the times very trying for him, and it was with joy that he welcomed an appointment as scientist to a Russian polar expedition, fitted out under the direction of Count Romanzoff, and commanded by Captain Kotzebue (1815-1818). The record of the scientific results of this expedition, as published by Kotzebue, was full of misstatements; and to correct these, Chamisso wrote the 'Tagebuch' (Journal) in 1835, a work whose pure and plastic style places it in the first order of books of travel, and entitles its author, in point of description, to rank with Von Humboldt among the best writers of travels of the first half of the century. After three years of voyaging, Chamisso returned to Berlin, and in 1819 he was made a member of the Society of Natural Sciences and received the degree of Ph.D. from the University of Berlin, was appointed adjunct custodian of the botanical garden in New Schoeneberg, and in September of the same year he married Antonie Piaste.