The hour arriving for opening the Convention, and Mr. Horton having entered the hall, stood up to offer prayer just as the clock struck twelve. Strongly and fervently his words came up, breathing petitions for the peace of his country and the deliverance of the oppressed. God heard him, but with that prayer His servant's work ended, and then He gave him for a little while to the cruel wrath of his enemies, that He might make that wrath praise Him. Immediately on the sounding of the stroke of noon from the city clocks, and simultaneously with the opening of Mr. Horton's prayer, the armed police filed out of the several stations, three hundred strong, and marched toward the Institute. Some of them entered the hall during the prayer, a mob in the meantime rapidly collecting round the door, and hardly had the good man uttered the closing "amen" when a miscreant fired a bullet at his head. There could be no longer any doubt of the intentions of the officers and the mob. The latter assailed the windows and crushed in at the doors. "Kill him! kill him!" they yelled. "Shoot every cursed Yankee in the house!" Just then all the bells in the city began to toll. It was the preconcerted signal of slaughter, and now the horrors of the day began. The disloyalist ruffians rushed in with pistols, knives and clubs, and commenced their appointed work of murder. Resistance was hopeless. The Convention broke up in the wildest confusion, some of its members falling dead, and many mortally wounded in the hall, while a few who could, fled. The Union men saw that they were doomed. Instead of protecting them, and arresting the rioters at the firing of the first shot, as with their force they could easily have done, _the police headed the attack_, and there is reason to believe that one of their number fired the first shot. Mr. Horton received five balls in his body, and fell. These balls were fired by policemen. Not satisfied with their work, they seized him, battered his head with their billies, stabbed him, kicked and dragged him on the pavements to the first station, the mob following behind, cursing, beating and trampling him with their shoes. Thrusting him into a cell, he was left mangled and senseless. Meantime the shopkeepers of the city had closed their stores, and strolled about, gratified spectators of the fiendish carnival, greeting the murderers of Horton, and every squad of policemen that passed them dragging a bleeding loyalist, with shouts of "Good! good! Kill the white nigger." Around the Mechanics' Institute and in the adjacent streets upwards of one hundred negroes lay weltering in their blood, and the dead carts drove by loaded with warm corpses and bodies of the wounded still writhing with life, all tumbled indiscriminately together.