Stuart, of Alexandria. I sent telegrams early this morning embodying the most important information, one to yourself and one to General J. E. Johnston. I sent by courier a copy of the statement of Mr. Stuart to General Johnston, and have directed the reverend gentleman to be brought in that we may hear what more he has to say.

Very respectfully and truly, yours,

G. W. SMITH,

Major-General, Commanding.

Memorandum of a conversation held by Captain B. B. Douglas, Company H, Ninth Virginia Cavalry, with the Rev. K. J. Stuart, late of Alexandria on Saturday, the 5th of April, 1862.

Mr. Stuart is an Episcopal clergyman, and was recently arrested in Alexandria while officiating in the pulpit for refusing to offer prayers for the President of the United States. He escaped in company with a young man named Brent on Thursday night, the 3rd instant, disguised as sailors, and landed on Friday night in King George Country, Va., just above Mathias Point.

Plans and policy of the enemy.-Early in February last Mr. Stuart was in Washington City, where he saw and conversed with Major Lee, Judge Advocate-General of the Federal Army. Major Lee said that in thirty days from the date of the conversation the plans of the Federal Government would be fully developed. They consisted in part of a grand and powerful movement against Centreville and the whole Potomac line of defense. The Government had called into play its every resource so as to insure success, and had proceeded on a scale of expenditure so vast that its means and its credit were for the present all absorbed or exhausted. It was impossible to renew an effort of such magnitude if failure ensued, unless the new phase of policy to be adopted in such an event gave fair promise of success.

This new phase consisted in directing all their efforts to detaching the border States form the Southern Confederacy and proposing peace on the basis of the independence of the rest.

The States and parts of States to be detached were Delaware, Maryland, Western Virginia, Kentucky, and Missouri; also, if possible, Tennessee. The means to this end were the destruction of slavery, the expulsion of all secessionists, or their exclusion from the pulpits, the courts, the practice of medicine, the marts of trade, &c., and the introduction of a more subservient element, by which the Unionists should obtain preponderance at the ballot-box.

Mr. Stuart says that the greatest dissatisfaction exists toward General McClellan for allowing General Johnston to escape the toils so laboriously and at such heavy cost prepared for him. In the North the move is looked upon as one displaying the most masterly strategy, as frustrating the anxiously expected denouement of their gigantic schemes, and extremely disastrous to the Federals.

An officer in the Treasury Department, noted for the general accuracy of his information and in a position to be well informed, told Mr. Stuart that General Johnston's move had cost the Federal Government $ 100,000,000, and that the daily expenditure of the Government in its efforts to meet the change reached the enormous sum of $ 4,000,000.

Movements of the enemy.-Nearly all the forces in and near Washington, including Hooker's division, have been taken to Old Point. General McClellan has himself gone thither, passing down the river, as Mr. Stuart had every reason to believe, on Friday last.