The protection against the ice has proved its value completely. The ice as it moves becomes crushed against the defence, and then has its advance impeded by the shoal upon which it grinds and packs, to form in itself a barrier and ice-breaker against other approaching ice-fields. This structure was soon submitted to a stern test to prove its efficacy. In the spring of 1875, when the keepers returned to the lighthouse--the light, in common with all other beacons guarding the Great Lakes, is shut down during the winter, when navigation is closed--they found the tower unapproachable. The ice-shove had jammed, packed, and been frozen into a solid berg to a height of 30 feet, of which the tower itself formed the core. The doorway was buried to a depth of 7 feet, and the keepers had to carve their way with pickaxes to the entrance. Owing to the success of the design for the Spectacle Reef lighthouse, which ranks as a striking engineering achievement, it was adopted for the Stannard’s Rock tower. This ledge rises from the water 28 feet from shore, and the plant and tackle which were employed in connection with the first-named structure were utilized in this undertaking. The tower is 191 feet in height, and the light can be seen for about twenty miles. During the past two or three years the United States Government has erected two other noble lighthouses in Lakes Superior and Michigan. The first warns all and sundry off a rock having three ugly pinnacles projecting above the water, and known as the “Rock of Ages.” This danger stands right in the steamship tracks between Port Arthur and Duluth, off the western end of Isle Royale. The engineers selected one of the pinnacles as the base for the tower, decapitating the projection to 12 inches above mean low-water, so as to secure a sufficiently large and level plinth. On this bed a cylindrical foundation pier, of massive proportions and strength so as to withstand the ice action, was planted, to support a lofty tower in reinforced concrete. The building has seven floors, one being set aside for housing the two twenty-four horse-power oil-engines which are used to drive the air-compressors for the fog-siren. The light is 125 feet above water-level, and gives a double flash at ten-second intervals, which can be picked up twenty-one miles away. This tower was erected in a very short time, the work, commenced in May, 1907, being completed, except for the installation of the permanent lens, thirteen months later. The optical apparatus was fixed and the light shown first on September 15, 1910.