On the 5th of April, in a letter to his Excellency Sir Charles Whitworth, the British minister at Petersburgh, Lord Nelson thus writes respecting Malta--We certainly have, at an expence of fifteen thousand pounds a month, so closely blockaded the port of La Valette, that the appearance of the Russian troops on the island must insure it's fall in a week, if famine does not force it's surrender before their arrival. The garrison are mutinous, and in dreadful want of provisions. The scurvy cannot be checked. His lordship then observes, that his anxiety to get possession of Le Guillaume Tell, and two frigates, which escaped after the battle of the Nile, will not be doubted; and that these ships, but for our close blockade, would probably have long ago been in France: all which, he begs, may be submitted to his Imperial Majesty, the Emperor of Russia. He has, he adds, given directions to Captain Ball to co-operate in the most cordial manner with the Russian troops; who so ably conducted himself, not only as a sea-officer, but as conciliating the affections of the Maltese, that he was, unanimously, by the islanders, and with the approbation of his Sicilian Majesty, elected their general and chief. His lordship trusts that, should the order be restored, Captain Ball would be a knight of it; "for a more gallant, able officer, does not grace this world. I feel," continues he, "I have said a great deal; but, with my honour, I pledge myself for the truth of it." Then, with the most consummate address, Lord Nelson proceeds to remark--"His imperial majesty will know, that the poor islanders have often, in their distress, and as a mark of their gratitude, offered--as far as they could--themselves for subjects of our king, and made their request to his Sicilian Majesty; but both Sir William Hamilton and myself, knowing that no views of individual aggrandizement actuate the breast of our gracious sovereign, have invariably refused every offer of that nature: but, in the present situation of his Sicilian Majesty, and by his desire, his colours and the British flag fly together, to mark that Great Britain protects the flag of his Sicilian Majesty. It is proper in this place to mention, as the heart of the emperor overflows with justice, that in many instances the islanders have been grievously oppressed by the order; probably, more by their consummate pride, than by a wish to oppress. I know, it is only necessary to mention this matter, for the consideration of the present illustrious Grand Master, to have it remedied; by which, a brave and industrious people will be rendered happy." His lordship concludes this exquisite proof of diplomatic dexterity, with observing, that he impatiently waits the arrival of the Russian troops; by nine or ten thousand of whom Naples would be recovered in a week, and his imperial majesty have the glory of replacing a good monarch and an amiable queen, again on their throne.