The Durham boat Mulcaster, Thomas Chambers master, bound from Prescott to Montreal, with a valuable cargo of Ashes, Flour, Butter, &c. &. &. was upset in the Cedar Rapids, on Thursday evening. The cause of this disaster was the breaking of the steering pin, which rendered the rudder useless, and the boat in consequence became unmanageable. This was discovered when about the centre of the Rapids, and notice thereof instantly given; the boat was then suddenly thrown upon her beam end, in which situation she remained for about five minutes, when the Master cried out to all hands to take care of themselves, as she would either right herself, or be thrown bottom upwards, on striking the next shoal, which took place almost immediately the whole of the passengers and crew, consisting of about 24 in number including the Pilot, were precipitated into the water some gained a situation on the bottom of the boat, and assisted in picking up the remainder, with the exception of James O'Hare, a native of Ireland, who was on his way home, who imprudently jumped overboard before the boat upset, in expectation of being able to gain the land by the assistance of an oat, but was unfortunately drowned. When the first alarm of danger was given a woman on board named McInroe, sprang from the cabin, and partly ascended the ladder leading to the deck, but instantly returned for her infant child, with which she was swept overboard by the overflowing water, as was luckily for her the companion of the cabin upon which she managed to obtain a seat, and with her child in her arms was providentially borne through the remaining part of the rapids, until picked up by a canoe in perfect safety. About two thirds of the cargo has been got on shore, but all in a damaged state. The trunk belonging to O'Hare was found, it contains about 50l. in cash, and some clothing, which are in charge of Captain McMaster at Lachine.