Army, I resumed command of the Department of the West the 11th instant. On my arrival at Saint Louis I found very great excitement prevailing throughout the community in consequence of the capture, on the 10th instant, of the brigade of Missouri militia, under the command of Brigadier General D. M. Frost, while in camp near this city, by the United States forces, under the command of Captain N. Lyon, Second Infantry. I am informed that a detailed report of that affair was forwarded previous to my resuming command of the department, but I deem it proper to state that the conduct of Captain Lyon on the occasion meets with my entire approval.

As serious apprehensions were entertained yesterday morning that the excitement existing in the city would result in an outbreak in the course of a few hours unless allayed, I deemed it necessary to issue a proclamation, of which the inclosed is a copy, and which, I am assured, was well received and had the effect to tranquilize the public mind. I also ordered up from the arsenal some 250 regular troops, with four pieces of artillery, to aid the civil authorities in the preservation of the public peace. I am happy to add that all indications of the threatened disturbance have disappeared.

I am, sir, very respectfully, your obedient servant,

WM. S. HARNEY,

Brigadier-General, Commanding.

[Inclosure.]

PROCLAMATION.

MILITARY DEPARTMENT OF THE WEST,

Saint Louis, Mo., May 12, 1861.

I have just returned to this post, and have assumed the military command of this department. No one can more deeply regret the deplorable state of things existing here than myself. The past cannot be recalled. I can only deal with the present and the future. I most anxiously desire to discharge the delicate and onerous duties devolved upon me so as to preserve the public peace. I shall carefully abstain from the exercise of any unnecessary powers and from all interference with the proper functions of the public officers of the State and city. I therefore call upon the public authorities and the people to aid me in preserving the public peace.

The military force stationed in this department by authority of the Government, and now under my command, will only be used in the last resort to preserve the peace. I trust I may be spared the necessity of resorting to martial law, but the public pease must be preserved, and the lives and property of the people protected. Upon a careful review of my instructions I find I have no authority to change the location of the Home Guards. To avoid all cause of irritation and excitement, if called upon to aid the local authorities in preserving the public peace, I shall in preference make use of the Regular Army.

I ask the people to pursue their peaceful avocations, and to observe the laws and orders of their local authorities, and to abstain from the excitements of public meetings and heated discussions. My appeal I trust may not be in vain, and I pledge the faith of a soldier to the earnest discharge of my duty.

WM. S. HARNEY,

Brigadier-General, U. S. Army, Commanding Department.