Twenty six letters sent by William Dawes to Nevil Maskelyne, covering his initial preparations for departure, his passage via Rio de Janeiro, the establishment of the observatory at Port Jackson, his work there, and his eventual return on HMS Gorgon six years later.
The letters include detailed accounts of setting up the observatory in Sydney where he hoped to observe a comet, and of the difficulties encountered there (particularly shortages of supplies and Dawes' own disagreements with the Governor, Arthur Phillip).
The series also includes five letters from William's father, Benjamin Dawes, petitioning the case for his eventual return, including a letter in which he describes the rations at the settlement, where food supplies were running short after the loss of HMS Sirius [RGO 14/48: 305-306].