Additional details--The Pampero's name changed to that of the Liberator--Her return to Key West under the Cuban Flag--Conduct of the Collector--Letter from Gen. Lopez--His reception.

The following interesting news is extracted from a private letter, received on Saturday by a gentleman in this city from one of Gen. Lopez's friends in Savannah.

SAVANNAH, Aug. 25th, 1851

In one of the Florida steamboats the captain of the "pampero," now the "Liberator," arrived here yesterday. From him we learn that the General went to Key West, for the double purpose of * * * * and of ascertaining from the fishermen the position of the Spanish cruisers. As a friend in Key West writes to us who spoke with the General on the night of the 9th, he determined to make his landing where he did make it, in consequence of the satisfactory information which there received, as well of the condition of the Vuelte Abajo as of the position of the Spanish vessels.

While on his way, opposite to Havana, the engine got out of order, and before the injury could be repaired two hours were consumed, within which time the current carried the steamer in sight of the Moro. From it she was signalized. They were near enough to distinguish with the glass men on the shore, and the water dashing up against the rockey foundations of the Moro. Two Spanish vessels of war, one of them the La Perla passed them at little more than a mile's distance. By these the Pampero was undoubtedly taken for a steamer bound into Havana.

As soon as the derangement of her machinery was repaired she got up stream, and the vessels of war observing her heading to the westward instead of going in towards the city suspected and made an attempt to follow her; but it was then too late, the Pampero was going very fast, and they went into Havana. It seems that the Cincinnati, which was despatched from New Orleans by the Spanish Consul 30 hours before the Pampero, did not reach Havana till after Lopez had effected his landing, notwithstanding the stoppage at Key West. The same evening she was off Ortigos at a league from Bahia Honda, from which place the General dates his letter written back by him to ________. Early on the morning of the 11th, the steamer being aground in the inlet (ensenada) of La Ma Cata, he effected his landing with the small boat of the steamer, and others brought from the shore; not consuming more than two hours and a half in the operation, notwithstanding that mishap.

At seven, owing to the lightening of the vessel and the rise of the tide, she floated again, and soon after put to sea. She was short of coal, the boiler made but little steam, and she went slowly; and while she was taking more coal at Key West, some days were spent, and she did not reach the coast of Georgia until Friday, the 22d. * * * *

Before the Liberator quitted the Cuban coast, her captain saw hundreds of the peasantry flocking down to the shore, bringing horses, fruit, vegetables and fresh meat, to mount and supply the General's men. He no doubt moved slowly towards Bahia Honda, after some rest at Las Pozas, which is about two miles from La Mulata, for till the 13th, he was not attacked at San Miguel de los Caldereteros, a village about a mile from Bahia Honda, 16 from Las Pozas. I presume his second engagement was between Bahia Honda and San Diego de Nunez, a town six miles to the East, since the General directed a flank movement with 50 men in boats, undoubtedly to cross the open space of sea from one part of the Bay to another, at the points of which are situated the two villages named. These fifty men were taken by a steamer and shot in Havana."

When the Liberator returned to Key West, she came in with the Cuban Flag, and with papers from Gen. Lopez. These were handed to the Collector, who withdrew to reflect upon his course, the steamer meanwhile remaining at the wharf, with her flag flying. After a time, a friend having brought notice that the Collector, intended to detain her, Captain Lewis moved off beyond that officers reach. The Collector and one other persons are understood to be the only two men at Key West unfriendly to the Cuban revolution. By and by he will be made to treat a little more respectfully the flag which the Liberator has had the honor of thus inaugurating in an American port.