Lady Mary wrote many letters to Francesco Algarotti in English and in French after his departure from England in September 1736. In July 1739, Lady Mary departed England without her husband ostensibly for health reasons, possibly from a disfiguring skin disease, and declared her intentions to winter in the south of France; after she left England, she and her husband never met again. In reality, she left to visit and live with Algarotti in Venice. Their relationship ended in 1741 after Lady Mary and Algarotti were both on a diplomatic mission in Turin. Lady Mary stayed abroad and travelled extensively. After travelling to Venice, Florence, Rome, Genoa and Geneva, she finally settled in Avignon in 1742. She left Avignon in 1746 for Brescia, where she fell ill and stayed for nearly a decade, leaving for Lovere in 1754. In the summer of 1756, Lady Mary travelled to Venice for an undisclosed business errand. After August 1756, she resided in Venice and Padua and saw Algarotti again in November. Throughout the time, Lady Mary exchanged letters with her daughter, Lady Bute, discussing topics such as philosophy, literature, and the education of girls, as well as conveying details of her geographical and social surroundings.