A protest, signed by the thousands of men taken at Arkansas Post, now exchanged, against being kept on this side of the Mississippi, has been received. The protest was also signed by the members of Congress from Texas, Louisiana, Arkansas, and Missouri. Capt. Causey, of the Signal Corps, writes that there are only a few battalions of the enemy on the Peninsula; but that rations for 40,000 men are sent to Suffolk. Gen. Lee announces the crossing of the Rappahannock at Port Royal (which the Yankees pillaged) and at places above Fredericksburg. Gen. Stuart is hovering on their flank. A great battle may happen any moment. L. E. Harvey, president of Richmond and Danville Railroad, asks for details to repair locomotives, else daily trains (freight) must be reduced to tri-weekly trains--and then the army cannot be sustained in Virginia. Hon. Mr. Garnett asked (and obtained) permission for a Mr. Hurst (Jew?) to pass our lines, and bring Northern merchandise to Richmond for sale. He vouches for his loyalty to Virginia. Congress has before it a bill rendering this traffic criminal. MAY 2D.--The awful hour, when thousands of human lives are to be sacrificed in the attempt to wrest this city from the Confederate States, has come again. Now parents, wives, sisters, brothers, and little children, both in the North and in the South, hold their breath in painful expectation. At the last accounts the two armies, yesterday, were drawn up in battle array, facing each other. No water flowed between them, the Northern army being on this side of the Rappahannock. We have no means of knowing their relative numbers; but I suspect Gen. Hooker commands more than 100,000 men, while Gen. Lee's army, perhaps, does not exceed 55,000 efficients. Accounts by passengers, and reports from the telegraph operators at the northern end of the line, some ten or twelve miles this side of the armies, indicate that the battle was joined early this morning. Certainly heavy cannonading was heard. Yet nothing important transpired up to 3 P.M., when I left the department, else I should have known it. Still, the battle may be raging, without, as yet, decisive result, and the general may not have leisure to be dictating dispatches. Yet the heavy artillery may be only the preliminary overture to the desperate engagement; and it seems to me that several days might be spent in manoeuvring into position before the shock of arms occurs, which will lay so many heads low in the dust. But a great battle seems inevitable. All the world knows the fighting qualifications of Gen. Lee, and the brave army he commands; and Gen. Hooker will, of course, make every effort to sustain his reputation as "fighting Joe." Besides, he commands, for the first time, an army: and knows well that failure to fight, or failure to win, will consign him to the same disgrace of all his predecessors who have hitherto commanded the "Army of the Potomac."