| Description | Summarised “The custom of Cornwall, upon deep mines, is to erect engines of such a size as to go half as deep again, i.e. if a mine was 40 fathoms below adit, then to erect an engine to go 60 fathoms and to begin with 2/3 of the power. 8 fathoms increases power 1 lb. per inch. Concerning the yearly income from engines. Hornblowers have nearly finished their engine.” |