Letters from Mary Cornwallis Herschel, to John Herschel Letters from Mary Herschel to John Herschel, on his travels to make observations for the Great Trigonometrical Survey of India. This set of letters corresponds to John Herschel's arranged as HSF/2/3. They relate to one single period of separation between the two, in early 1872, during which they agreed to write on alternate days, so that each would contribute a letter at two day intervals. Th e letters are occasionally initialled 'MCH', but generally, neither correspondent is named. November 1871-April 1872