One of the most important items of intelligence this morning, is contained in the report of the New Orleans correspondent of the New York Herald, that the long anticipated attack on Mobile had commenced, and that Admiral Farragut successfully passed forts Morgan and Gaines on the 28th ult., entering Mobile Bay. The New York Tribune, however, discredits this intelligence. On the other hand, additional color is given to the original report by advices received at Washington from Admiral Farragut of the 26th., when he reported himself ready for the attack, and only waiting for the land forces to get into position. There are indications that the land movement would be made from Pensacola. Gen. Rousseau's late raid, in which he effectually broke up railroad communication between Atlanta and Montgomery, had an immediate connection with this movement. Further advices from that quarter will be looked for with eager interest.
The Pennsylvania invasion business is still in an inexplicable muddle. The condition of affairs there seems to be growing chronic, and the country generally is rapidly becoming indifferent to the cry of helpless despair coming up from Pennsylvania farmers who see their riches vanishing in the direction of the Shenandoah Valley, and still do little or nothing for their self-protection. The latest advices by our Saturday night dispatches are to the effect that the rebels have evacuated Hagerstown, and are retreating down the Potomac, though the news may be contradicted by the report of another advance within twenty-four hours. Altogether, we think it will be found that this formidable rebel invasion has had the two-fold object of securing the crops in the Shenandoah Valley and of recruiting the rebel army by conscription. These objects having been accomplished, the rebels are probably about ready to retire, and their last advance is for the purpose of masking their real movements. Their retreat may be hastened by the movements which Gen. Grant is understood to be making to attack them.
The disaster to Gen. McCook's command in Georgia, after destroying the Atlanta and Macon Railroad, proves to be much less than first reported — his loss having been reduced to 800 men. The rebel report of the surrender of Gen. Slocum with 5,000 men in Saturday's dispatches, doubtless refers to this attack on McCook, and Stoneman's name should be substituted for that of Slocum. The report, however, is believed to be a rebel canard with a very small basis of truth.
The rebels are reported to have met with a repulse in an attack upon Fort Smith, Ark. There is also a report of a rebel defeat near Osceola, in the same State.