 During the late 19th century, arsenic production came into ascendancy with mines in the east of Cornwall and West Devon supplying half the world’s demand.The early 19th century also saw a revolution in steam engine technology which was to radically transform hard-rock mining fortunes.The high-pressure expansively operated pumping engines developed by the engineers Richard Trevithick and Arthur Woolf enabled mining at much greater depths than had been possible hitherto.