Washington, Feb. 28. Tho Richmond Seníinel of the 25th, says every chango of the seat of war begets an uneasiness and alarm iiot only in the new seetion invaded, but in tho country at large. Nobody seems to consider the relief extended to onc eection by the removal of the enerny's troopa to another, although the seetion rolieved be ten times as extensiva as tha country now invnd(-d. To make another rash aud desperate "on to Riohmond" our euemy has loosened hïa hold on the whole Mississippi Valley. He has also given up a tliird of Geo:gi, and a large part of Virginia. Slierman's movement is the key to the present attempt on Richmond. Defeat Sherman, and the Bchetce is at an end Defeat Sberman and the war at onoe wears a new and kindlior frout. Ho plajs boldlyfor a high stake ; if ha fails, bis own ruin will be corregpoudingly complete and rreooverable. The Whig says it would seem as if the Confedérate Senate was playicg into the hands of the enemy. Wo wau harmony, bold and concertod ac tion, uot a red-wall of State quarrels between the ootton oud border States. Such quarrels at fiuch a time, if not quiekly hushed, will nocessanly prove fulal tu our cause. The enemy will regard it as tha surost of al! signs of failure. Ï3ST I' is astimated that at the capture of Olmrlsetou ünd Port Andtrsnn, together with the oertain capture of Mobile before two weeks more, wül literato at least 25,000 men from the navy, who can be organized into corps for offensive operations 011 land.