The late plenipotentiaries, Captain Elliot and Sir Gordon Bremer, sailed from Hong-Kong, and finally took leave of China, three days after the departure of the expedition, on board the Atalanta steamer, which had become completely knocked up by her work in the Canton river. Their intention was to proceed as quickly as possible to England, by way of Bombay. The distance of Amoy from Hong-Kong is scarcely three hundred miles, and there were many good grounds for making it the first point of attack, as the expedition proceeded northward. It could not be doubted that the capture of this flourishing commercial city would be seriously felt by the Chinese government. The authorities had, within the last twelve months, spent enormous sums of money and incredible labour in the construction of batteries, which they deemed impregnable, and which were certainly capable of being stoutly defended. The harbour of Amoy is situated in the south-western corner of an island of the same name, which, together with another called Quemoy, occupies a considerable portion of a large bay, in which, however, there are also numerous smaller islands. Of these, the most interesting, in connexion with our present subject, is that of Kolingsoo, which is separated from Amoy by a narrow passage, leading directly up to the harbour. In fact, the possession of this island, which we still retain, gives us the complete command of Amoy itself, or rather of its town and suburbs. The scenery within the bay and about the town of Amoy is exceedingly picturesque, the appearance of the country being very mountainous and striking. Several considerable rivers pour their waters into the bay, and facilitate the communications with the interior of the country. The superiority of the harbour much exceeded the expectations of the officers. The town of Amoy, although possessed of great commercial importance, and very wealthy, is by no means a first-class city--it ranks, indeed, only as a principal third-class town--but its inhabitants are exceedingly enterprising and intelligent, and are remarkable for a certain disposition for emigration and colonization, as well as for their love of commerce. They were the principal colonizers of the flourishing island of Formosa, which lies opposite Amoy, extending itself along the coast for a distance of little less than two hundred miles; and they are to be found in great numbers in more remote islands, subject even to foreign dominion, such as Java, Singapore, Manilla, &c.