According to Jeffrey Murray in his book ‘Terra Nostra: The Stories Behind Canada’s Maps’. 2006. page.7 ‘In the eighteenth century, the cost of engraving a map in Britain, depending on its complexity, averaged from £2 to £30, but the Admiralty allowed Des Barres nearly £37. Although Des Barres left no indication as to how much time was spent engraving each of the 247 plates used in his Atlantic Neptune, it was not unusual for some of his contemporaries to take as much as a year and a half to two years to complete a complicated plate. One historian has suggested that, with a complex map, an eighteenth-century engraver might be expected to produce only one square inch a day’.