This was the first map based on a trigonometrical survey made by the Board of Ordnance. The drive to produce this map first arose from the need for an accurate map for national defence at the time of the Napoleonic wars and in 1801 it was published and made available tor civilians. The scale of the map was 1 inch to the mile. The section of the map around Leigh is shown below.
This map predates the powder mills but clearly shows the original flour mill at the foot of Weir Lane. There is neither tail stream nor obvious indication of a controlling sluice or weir. Presumably the flow in the mill stream was sufficient.