Besides the regular ship's crew, no one was received on board except Mr. Field and Professor Morse, who went as the electrician of the Newfoundland Company; and two officers of the Russian navy--Captain Schwartz and Lieutenant Kolobnin--who were permitted by our Government, as an act of national courtesy, to go out to witness the great experiment. The regulations of the navy did not admit correspondents of the press; but Professor Morse was permitted to take a secretary, and chose Mr. Mullaly, who reported for the New York Herald, and who had thus an opportunity to witness all the preparations on land and sea, and to furnish those minute and detailed accounts of the several expeditions, which contribute some important chapters in the history of this enterprise. The Niagara arrived out on the fourteenth of May, and cast anchor off Gravesend, about twenty-five miles below London. As it was the first time--at least for many years--that an American ship of war had appeared in the Thames, this fact, with her fine proportions and the object for which she came, attracted a crowd of visitors. Every day, from morning to night, a fleet of boats was around her, and men and women thronged over her sides. Everybody was welcome. All were received with the utmost courtesy, and allowed access to all parts of the ship. Among these were many visitors of distinction. Here came Lady Franklin to thank the generous nation that had sent two expeditions to recover her husband lost amid Polar seas. She was, of course, the object of general attention and respectful sympathy. While lying in the Thames, the Agamemnon, that was to take the other half of the cable, passed up the river. This was a historical ship, having borne the flag of the British admiral at the bombardment of Sebastopol, and distinguished herself by steaming up within a few hundred yards of the guns of the fortress. After passing through the fires of that terrible day, she was justly an object of pride to Britons, whose hearts swelled as they saw this oak-ribbed leviathan, that had come "out of the gates of death, out of the jaws of hell," now preparing to take part in achievements of peace, not less glorious than those of war. She was under command of Captain Noddal, of the Royal Navy. As the Agamemnon came up the river in grand style, she recognized the Niagara lying off Gravesend, and manning her yards, gave her a succession of those English hurras so stirring to the blood, when heard on land or sea, to which our tars replied with lusty American cheers. It was pleasant to observe, from this time, the hearty good-will that existed between the officers and crews of the two ships, who in their exertions for the common object, were animated only by a generous rivalry.