Our city was thrown into a fever on Monday, the 24th inst., by the rumor that the steamship Northern Light belonging to the Nicaragua Transit Company would be detained by the United States authorities. About one o’clock large crowds began to collect on pier No. 3, North river, from which the steamer was advertised to sail. Mr. MeKeon, United States District Attorney, and a number of his Marshals were present and proceeded on board of the Northern Light and took formal possession in the name of the government. The act of seizure was not known to the passengers till about half-past two, when the news was circulated and the greatest commotion took place in consequence. They were all acquainted with what had taken place on Saturday, but it was not believed that the government would order the vessel to be detained, and they supposed that she would sail at the appointed time. At two o’clock there were between four and five hundred persons on board the Northern Light, and over that number on the pier. Of the passengers, three hundred and fifty were, it was said, destined for the army of General Walker in Nicaragua. There were a considerable number of children also, and there was nothing in the appearance of anything on board to justify the suspicion that they were engaged in a hostile expedition. The greatest bustle and confusion prevailed on the steamer, which increased as the hour of departure drew near, and it was reported amongst the passengers that the vessel had been seized, and should not sail that day.