On the west end of this island there was a partly-finished fort, occupied by Lieutenant Buchanan and one hundred and seventy sailors and marines, with several ship guns in position. The rebels had evacuated the island in September, destroying what they could not carry away with them. General Phelps, on assuming the command of Ship Island, published a proclamation “To the loyal citizens of the South-west,” in which he defined the political “motives and principles” by which his command would be governed. He then at the very opening of his address, declared that every slave State admitted into the Union since the adoption of the Constitution, had been admitted in direct violation of that instrument. That every slave State that existed as such at the adoption of the Constitution, was by that act placed under the “highest obligation of honor and morality to abolish slavery.” The rest of the “proclamation” was in harmony with these statements. General Phelps made an official report of his expedition to General Butler, who reported the facts to the Adjutant-General of the United States. General Phelps was commended for the successful manner in which he had performed his military duties, but his proclamation was pronounced superfluous and uncalled for. The occupancy of Ship Island being secured, the forces remained in undisturbed possession, awaiting the future movements of the commander of the expedition. ENGAGEMENT AT MOUNT ZION. DECEMBER 28, 1861. On the 23d of December, General Prentiss, commanding the army of Northern Missouri, having his headquarters at Palmyra, received orders to disperse a body of the enemy’s forces that had concentrated in Boone County. In pursuance of his instructions he started on the following morning with two hundred of the Third Missouri Cavalry, Colonel John Glover, and five companies of Sharpshooters, under Colonel Birge, and arrived at Sturgeon on the evening of the 26th. During the following day, having learned that there was a concentration of rebels near the village of Hallsville, in Boone County, General Prentiss sent forward one company of cavalry, commanded by Captain Howland, to reconnoitre in that vicinity. Captain Howland proceeded to Hallsville, but found no rebels. After proceeding about two miles beyond, his advance guard encountered the rebels in force, commanded by Colonel Dorsey. Captain Howland endeavored to draw off his company, having taken nine prisoners, but was overpowered. Being wounded, and having lost his horse, he was taken prisoner, with one private of his company. The remainder of his men made good their retreat, arriving at Sturgeon at nine o’clock, P. M.