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} 190 . LAKE MICHIGAN. is sounded a steam-siren, giving blasts of 5 seconds at intervals of 30 seconds. Cana Island light-house, S. by W. 2 W., 14% miles. Rocky spits extend from this island to the southeast and southwest for one quarter of a mile. Nine-foot Shoal (Porte des Morts Passage).--Black 2d- class nun buoy in 18 feet of water. Marks the southeast end of the 9- foot shoal in the Porte des Morts passage, on the southwest side of the channel. Vessels bound through the. passage from Lake Michigan can steer N. W. 4 W. when abreast this buoy. Porte des Morts light-house, N. E. by E. 4 E., 12 miles. 'Northwest point of Plum island, N. ~ W., 22 miles. Outer Shoal buoy, 8. 8. E. + E., 3 miles. To Enter Green. Bay through Death's Door (Porte des Morts) passage, when 2 miles 8. S. E. 4 E. of Pilot Island light, steer N. W. 4 W. until fairly into the bay. ' Detroit Island Passage.--Red spar buoy in 11 feet of water. On the southwest point of the shoal, which lies in the passage-way be- tween Detroit and Plum islands. The charts give 12 feet as the least depth of water on the shoal, but spots have been found with only 10 feet of water on them. The anchorage between Detroit and Plum islands is a safe one, and is frequently used, during eastern gales, by vessels bound _ from Green bay into Lake Michigan. The range between the west point _ of Washington island and Pilot Island light leads fair between this buoy and Plum Island buoy, and in good water. / Porte des Morts Range Lights.--To be built on the south- west side of Plum island. Z Plum Island.--Black spar buoy in 14 feet of water. Marks the northeast point of the shoal extending to the northward from Plum island. It can be passed close-to from the northward, but on approaching it from the westward it should be given a berth of at least a half of a mile. Northwest end of Plum island, 8S. W. + W., + mile. : Nine-foot Shoal (Rock Island Passage),--Red, 3d class can buoy in 21 feet of water. On the southwest side of the small 9-foot shoal in the passage into. Green bay, between Rock and St. Martin's island, about 2 miles distant from the south end of St. Martin's island and 24 miles from Rock island. The shoal is of small extent, with deep water close-to. .The usual passage-way is between the buoy - and Rock island, and, unless familiar with the locality, vessels should not pass to: the northward of the buoy. Pottawatomie light-house, 8. W. by W. 4 W.., 8 miles. Southeast point of St. Martin's island, N. by E. 4 E., 24 miles. Fish island (awash), S. by E., 3% miles. , | POTTAWATOMIE, OR ROCK ISLAND LIGHT-STATION.-- A fixed white light, 4th order, visible 194 miles. Lantern on gray stone dwelling, 34 feet high, light 137 feet above lake level. On the north point of Rockisland. A. guide into the passage between Rock and St. Martin's islands. Off the southeast point of Rock island there are two dangerous reefs, with rocks above water or awash, bearing from the point E. by 8. 28. and 8. 8. E. 4 E., distant respectively about 2+ and 34. miles. 'There isa passage-way between these shoals and Washington and Rock islands. Vessels from Lake Michigan for Green bay can bring the light to bear, in . 18 fathoms water, from W. %N. to W. by 8. +8,, and stand for it, hauling half a Be mile to the northward as they approach the light, with the light abeam when stand- a ing for the westward. Southeast point of St. Martin's island N. E. 2 N., 4% miles. et North point of Boyer's bluff, W.258., 54 miles. Point Peninsula light-house, N. Desi LN. W.4W., 174 miles. : eS POVERTY ISLAND LIGHT-STATION.--A flashing red light. 4th a order, visible 152 miles; the interval between flashes is 15 seconds. White en) tower, 65 feet high, connected by a covered way with white dwelling. On the south point of Poverty island. A guide to the passage into Green bay, between the ; : Gull Islands and Poverty island. Heavy draught vessels bound into Green bay Pie 2 should keep at least 3 of a mile south of Poverty Island light, then steer midway be- a o tween the buoys on Gravelly Island and Poverty Island shoals about N. W. + W be , | a *3