A great Union demonstration took place in San Francisco, Cal. Nothing like it was ever seen there before. Business was totally suspended; all the men, women and children of the city were in the streets, and flags waved everywhere. Three stands for speakers were erected, and Senator Latham and McDougall, General Sumner, General Shields, and others addressed vast audiences. The spirit of all the addresses, as well as of the resolutions adopted, was: the Administration must be sustained in all its efforts to put down secession and preserve the Union complete. A procession marched through the principal streets, composed of thousands of men on horseback, in carriages and on foot, and embracing all the military and civic organizations of the city. All political parties joined in the demonstration.--Alta Californian, May 12.
The Savannah Republican of to-day says: “ we have conversed with a gentleman who has just returned from the camp at Pensacola and brings the latest intelligence.  As details are not to be expected, we may state generally that the condition of the troops and fortifications is all that could be desired. Gen. Bragg has proved the very man for the work, and the volunteers lend a ready hand to carry out every order. Pickens is covered by our batteries on three sides. There are eight between the Navy-Yard and Fort Barrancas, four between the latter and the light-house, and a formidable mortar battery in the rear of Fort McRae. There is also a heavy mortar battery in the rear of Barrancas. All these works have been erected by the hands of the volunteers, and are armed with the very heaviest and best of artillery. The channel on a line between McRae and Pickens has been obstructed by sinking a number of small vessels. It was supposed that every thing would be complete by the middle of the coming week, after which we shall have a bombardment that will be worthy of record. Pickens must fall, and the more men they put in it the greater will be the destruction. Besides Pickens, the enemy have thrown up a battery on the island some five miles from the fort, which they are now engaged in arming for the struggle. Some hundred or more horses can be seen on the island, and seven ships of war and transports are lying off, something less than a mile from the shore.”
The Fifth Regiment of N. Y. V. M. arrived at Washington from Annapolis, Md.--National Intelligencer, May 13.
A large meeting took place at Wheeling, Va. Hon. John S. Carlile and Frank Pierpont spoke. Mr. Carlile took ground in favor of separation from Eastern Virginia, and was rapturously applauded. He proclaimed that while there should be no coercion to go out, there should be none to prevent remaining in the Union. Virginia, he said, owed forty-nine millions of dollars; a debt incurred without benefit to Western Virginia; and he demanded to know by what right the citizens of this section should not be allowed to have an opinion of their own expressed and recognized in the. State councils, when the question of allegiance was discussed. Allegiance was first due to the Federal Government if there was no interference with State rights.--N. Y. Times, May 12.
The First Regiment of Pennsylvania Infantry, under command of Colonel Lewis, arrived at Washington.--N. Y. Tribune, May 12.
This afternoon, a large body of the Home Guards entered St. Louis, Mo., through Fifth street, from the Arsenal, where they had been enlisted during the day, and furnished with arms. On reaching Walnut street, the troops turned westward, a large crowd lining the pavement to witness their progress. At the corner of Fifth street the spectators began hooting, hissing, and otherwise abusing the companies as they passed, and a boy about fourteen years old discharged a pistol into their ranks. Part of the rear company immediately turned and fired upon the crowd, and the.whole column was instantly in confusion, breaking their ranks, and discharging their muskets down their own line and among the people on the sidewalks. The shower of balls for a few minutes was terrible. Seven persons were killed, and a large number wounded. To allay the ex. citement and restore confidence to the people, Gen. Harney issued a proclamation to the people of St. Louis and the State, which was posted throughout the city, expressing deep regret at the state of things existing, pledging himself to do all in his power to preserve peace, and calling on the people and public authorities to aid him in the discharge of his duties. He says the military force under his command will only be used at the last extremity, and hopes he will not be compelled to resort to martial law, but simply states that the public peace must be pre, served, and the lives of the people protected. He says he has no authority to change the location of the Home Guard quarters in the city, but to avoid all cause of circulation of the excitement, if called upon to aid the local authorities, will use the regular army in preference. In accordance with this proclamation, a battalion of regulars was sent to the city and placed under the direction of the Police Commissioners to act as a military police corps.--N. Y. Times, May 13.
The United States Steam Frigate Niagara arrived off the bar of Charleston, S. C., and began the blockade of that port.--(Doc. 155.)
Six companies of volunteers left Buffalo, N. Y., for the rendezvous at Elmira. Buffalo has so far sent to camp ten companies of volunteers. The Third Company of the Broome Co. N. Y. Volunteers, under command of Captain Peter Jay, took their departure from Binghamton, N. Y., for Elmira. They were addressed by the Hon. Daniel S. Dickinson, Tracy R. Morgan, and  others. They vowed to stand by the Constitution and the Union as long as one star remained.--N. Y. Times, May 12.
Schooner G. M. Smith, prize to the frigate Cumberland, arrived at New York in charge of prize--master Thos. Chisholm.--N. Y. Times, May 12.