This is the page where I believe the error was made. The page serves to convert Departure to the change in Minutes of Longitude, known as D.Long. It covers Latitudes of 42° and 48°. The conversion is done using the correct columns, which are those named in italics and marked with brackets. For 42° the columns are inspected working down the page. For 48° they are read from the bottom. When used to convert Dep to D.Long, the bold column headings are ignored. The key figures are indicated.
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