LAKE PIRATES.--We learned from the Detroit papers that the gang of gew-gawed gentry who were some weeks since engaged a number of days at Waterloo, opposite this place, in making preparations for some secret expedition, and who attempted to pass themselves off as Mexicans, were arrested by the Sheriff of St. Clair county, aided by a number of citizens, on the night of the 20th ult., in the St. Clair river. The appearance, and conduct of the crew, all of whom were armed, and dressed in a uniform of blue trimmed with red, and who were sailing in an old black schooner, without a name, excited the suspicions of the citizens of St. Clair county. The Steamboat Gen. Gratiot was chartered and pursuit was made by the Sheriff and the citizens. Between 10 and 12 o'clock at night the suspicious vessel was overtaken, and hailed, but no satisfactory answers having been received, she was ordered along side. Her papers were demanded, but none were produced, whereupon the Sheriff served his protest, and the schooner with the crew were towed into Black River. Friday last was the day appointed for their examination.
LAUNCH.--A fine brig, called the Manhatten, was launched at Detroit of the 20th ult. She measures 93 feet length of keel; depth of hold 12 feet; and is said to be the largest square rigged vessel, and the best in model and strength, ever committed to the Lakes.
STEAMBOAT Buffalo.--The keel of a steamboat of 700 tons burden, to bear the above name, has been laid at Mr. Carrick's shipyard in Buffalo. Her dimensions, we learn from the Journal, will be 195 feet deck, and 29 feet breadth of beam. The engine, which has been obtained, is of 190 horse power, 16 feet [sic!] cylinder, and 9 feet stroke. She is designed to be completed and in readiness for the lake navigation next spring.