Richmond Whig

A SEA EXPEDITION ORGANIZING -The Hilton Head correspondent of the New York World says:

The preparations for movements long contemplated are now nearly completed, and the monotonous inactivity of the troops, who were obliged to watch the grand invested prize of Charleston from one of the barren sand islands near it, will be superseded by a fiery engagement not less important than any which have occurred on the Mississippi or the Peninsula. Although a immense force land and naval, are to participate in this coming conflict, I have reason to believe that the principal reliance is to be reposed in the route which has been chosen, and the tactics to be used. It is, perhaps, needless to state, that much depends on secrecy. The unauthorized publication of some facts connected with the expedition to which I allude, led to its temporary abandonment some weeks since. For that reason I shall be careful in what I transmit to you.

It is not, however, a breach of prudence to state, what is already known to the enemy, that for some time past troops have arrived here from Folly Island, for the purpose of joining an expedition which has been organized. The soldiers gladly left their unwholesome quarters, rendered occasionally peculiarly uncomfortable by the near descent of shot and shell, to which they could not even reply. A small force, however, remains on Folly and Morris Islands, sufficient for the purposes of defense, and to work the guns on the latter.

The expedition promises to be one of vast magnitude and truly equal, if no unforeseen event should intervene, to the great task it is designed to accomplish. Many of the vessels here are of light draught, and this circumstance has led some to believe that a portion of the fleet will sail up the Savannah river. This seems to be the impression of the rebels, who have increased the number of their batteries at Fort Jackson, and other forts near Savannah.

It is evident, however, that the enemy do not know the precise destination of the expedition, or at least, that they distrust their own speculative theories about it. They believe the most vulnerable portion of rebel dom will be selected; and from a prisoner who was recently captured near Fort Pulaski I have learned that the chivalry expect General Gilmore will make a grand attack on Charleston on the rear, and that the movement will be preceded by an expedition to the line of the Charleston and Savannah railroad, to cut off all communication and reinforcements between those cities.

The statement has been corroborated by the fact that Confederate sentinels now guard the portions of the road where the attack is anticipated.

The third theory of this expedition is, that it is intended for Mobile; that it is to be bombarded by the land and naval force that is, by the fleet of the harbor and the army which is to march overland from Pensacola, a distance of some forty miles. Those better informed in military circles repudiate this speculation, and profess to believe that the capture or destruction of Charleston and Savannah are intended by this movement. One important feature connected with it, which should not be overlooked, is that a large negro force is to accompany the expedition, which will be landed at various points where they can make occasional raids and bring to their ranks the slaves who largely abound in the interior.