Special observations were made by Mr. Darling in 1902 of magnetic variations over that portion of Lake Superior west of Devils Island, including regions of local compass attraction, which had been reported and which endangered navigation by drawing vessels from their courses. The resulting variations were mapped and published in the annual report of the Chief of Engineers for 1904 with diagrams and details of methods. The map was also redrawn by the Lake Survey and published in several annual editions of the Bulletin.