This fortification extends over the whole surface of Garden Key, and has an area over thirteen acres.  It is completely closed against surprise by escalade, though its armament is incomplete.  the first and second tiers, however, are finished, and the twelve outworks of bastions and curtains can mount three hundred and fifty guns.  The fort is further fortified by a wide ditch, reaching to the water, and protected by a strong counterscarp.  The guns of the fort command the inner harbor, but the outer bay is beyond their longest range.  The whole armament of the fort, when complete, is 450 guns, and the garrison necessary for its defense 1000 men.  Captain Meigs, of the engineer corps, is now in command of the fortress, and is in a position now, with Arnold's reinforcement, to defend it against any thing less than a regularly-equipped besieging army.

The following extract from a letter from Key West describes the reinforcement of Fort Jefferson by the Joseph Whitney: 'It was on the 18th of January that the Joseph Whitney was descried buy those maintaining possession of this important fortress.  The steamer did not show any flag, and her motions were watched with intense anxiety by Captain Meigs and his small band of laborers, composed of about fifty persons (part of whom were negroes), engaged in putting the fort in a state of defense.  No flag was flying from the fort, and the steamer's company were far from certain that the insurgents had not surprised and captured it.  Therefore, to ascertain how matters stood, a boat, in which were the first mate and Lieutenant Benson, went on shore to ascertain the actual posture of affairs with regard to the power holding the post.  The relief of Captain Meigs and party may be supposed of receiving the agreeable information that the steamer contained reinforcements with the view of preserving the fort to the United States, instead of a filibuster party to seize it for traitorous purposes.  His gratification was increased by the fact that a rumor had prevailed that a steamer, with an armed force of two hundred men, would be sent from some Florida port to wrest the fort from its rightful possessors.'"