Isabella Bishop regularly wrote to her younger sister, Henrietta Bird (1834-1880). These came to Henrietta, who lived in Edinburgh and then Mull, from all over the world, including Australia, America, Japan, China and the Malay Peninsula. Bishop described the letters as "diary-letters". In them she recorded in detail the stages of her travels. The letters are often extensive, the longest being 116 pages. Bishop used the details in these letters to produce her published works about her travels.