The William Hutton Papers relate primarily to geology and botany, and there is also much on the Newcastle Natural History Society, of which Hutton was the secretary. There is much correspondence with Alexandre Brongniart, H. S. Davis, John S. Henslow, John Lindley, David Milne, Roderick I. Murchison, George Steuart MacKenzie, and John Phillips.

These are primarily letters to Gray on various aspects of natural history, with many references to collections at the British Museum of Natural History. There are numerous letters from British scientists and from European colleagues. There are letters from Americans too, such as those from Agassiz which relate to his Florida expeditions and the creation of natural history collections.

There is correspondence concerning geology, botany, natural history, natural selection, evolution, British science and scientists, and other scientific topics. Most of the letters are written by Lyell, with a very few items by others.