The usefulness of cropmarks to archaeologists has largely been a fruit of inspection from aircraft, but the possibility was suggested by Rev. Gilbert White in "The Natural History of Selborne" (1789), in a note appended to his Letter VI, to Thomas Pennant, apropos of local people's success in searching for bog oak for house construction, by discovering these trees "by the hoar frost, which lay longer over the space where they were concealed, than on the surrounding morass." To White it suggested the query "might not such observations be reduced to domestic use, by promoting the discovery of old obliterated drains and wells about houses; and in Roman stations and camps lead to the finding of pavements, baths and graves, and other hidden relics of curious antiquity?"