For soine nionths the public haa been lookiug forward to the lauuch of the great opean iron ciad, Dictator. ïhe first attempt to lauuch her, almost a inonth ago, failed ; this secoud attempt has succeeded, and she now floats proudly upoa the water, DESCIUPTION 01' THE VüSSKL. It haviug beev frequeatly stated that the Dictator is an ocean iron-clad, the impression prevaila thst siie resembles New Irousides, and other vessels buil; for the purpose of going ta sea. This is not so. The Dictator has nene of the pharaphernaha of such cieeaii vessels as we are ia the habit of looking it in our harbors. Sbeiias none of the tall bul wurks, no masts, no riggiag, no capstan on deck, - notbing in fact, that looks like an ordinary ship. A tall man eould al most dip bis hands iuto the water from her deck, on which a game of base ball mlht be played even with the turret on. TUE HULL. ïhe ditnensions of the buil of the ves sel aro as follows : Extreme length over all 314 feet ; the aft overhang being 31 leet, and iorward overhang 13, it leaves 260 feet between perpendiculars ; extreme breadth 50, and depth 22L feet. Uulike the original monitors, and the tbe monitors ihat are now in course of ponstruction, the Dictator is almost exclusively iron, her frames, beams, te, being of that meta!. A person looking at her in the river forms no idea of her appearance when she is completely out of water. If any ordinary ship were lifted up, and an immense shelf of 11 feet of iron placed on the top of her deck overbangicg for a space of some four feet, on each -side, she would resemble the Dictatory. Every frame and beam is fasteued in the most secure manner, and we believe the bolts are all put in red hot, to render them suffieienlly tigbt. ïhe frames are put together in the game manuer as those of the Montawk and Passaic, but tbey are much more formidable, some parts of them being doublé. The skin of the ship - that is the coveriug of the frames - is of wood, put on in slabs lengthwise, each beam being about 14J inches square. These woodeu slabs are fagteped to the iron frauie with screw bolts, which have no nuts, thus rendering it impossible for any such occurreuce to take place as that by which the lamented Capt. Kogers lost his life Tbis wooden skin is no lcss than three feet eis inches in tb.ipk.uess. Tho magnitude of this surface can only be understood when we state tbat the huil of an ordiuary European steamer does not measure more thau eighteen to tweuty inches in tbickness; so that, without the out.side annor at all, the huil of the Dictator is nearly twice as thiok as t}jjt of the Persia. Botb fpi'ïfard and aft there are inserted in these wouden slabs immense blocks, pf jron to make them still more formidable and powcrfui. The lerigth of the huil, in the case of this vessel is the entire longth of the sbip, as a man can stand on tho extreme end of the bow and stern. Tiking intp account the usual slope of the sea, 'the Dictator oould not bc seeu f'our miles off. THE ARMOR. The arinor pf tbc original mouito consisted of 4 inches of iron, laid on in single plates, eacb one inch tbick. Tbat of the Warior consisted pf - ipches of iron laid on ir. a solid slab like our own iron-clad frigate lloanoke. Tho Fronch frigate Gloire had also 4J inches of iïenlaid in a solid slab. Now the Dictator bas on her pides alone 11 incbes of iron, and 5 inches of this is in one solid beam, Bomewhat liko the Warrior, the Gloire and the Jlpanoke, except tbat the plates of tbe latter were in very large slabs, wbile tboso of tbe Dictator are in beams 5 by 3 ÍDohVg, Over these 5 incb block of iron are six one-inch plates of iron ; making altogether aa armor of H inches of iron, the samo dmienatons as the armor of a turret of the original Monitor, the Passaic, Montauk, &c. The armor begius at the deck and goes down only six feet, which takes it about four feet below water ; so that the deck of the ocean iron-clad Dictator will only bo about two fcet over water. - Over this armor there is 22 feet of the ship, only two feet of which is covered by the 11 inches of iron mail, There are, therefore, 18 feet of the huil which bas only a skin ou of oue inch iron plate. The weight of the armor is about 525 tons - the burden of a pretty large sized steamer. At six cents a pound the armor would cost about $63,000, without workmanship. THE TURRET. There will be but one turret of an improved pattern. It was originally intended to cover it with twenty four inches of iron, but the perfectiou to whieh its construction has uow been brought will make fifteen inches sufficient. This is four iuches more than the armor of the original Monitor und the Passaic, and ten inches moro thau the armoi-ed sides of the vessels. The magnitude of the different beams and machinery of the turret isimpiense; and it is in this magnitude aud in its inipoved pattern that it chiefly differs from oíd túrrete, 'l'he apparatus for working the guns will be of a still newer principio than any yet carried out. The revolution in uaval artillery caused by the faoiljty with which four ov five men can work the old 15 inch gun, will be made still more startling when one or two men can eaaily handle the immense pieces of ordinance I to bo_ placed in the Dictator. The turret will be covered u aetiou wlieu necessary. The new bar, wbicf) was recentiy added to the turrets of the last batch of iron-clads since the disabling of the Passaic, will be adopted in the new turret on a mucü more improved principie. This bar is sixteen iuches thick, and fastened on with bolts. The gear of the turret is different from that of the other vessels, and is tnuch better, The turret complete will weigh almost 500 tons, or thereabouts, beiug almost as heavy as the entire artnor of the vessel. It is not on board at present, but will bo put in itsïfcice immediately, as it is corupleted. TOE RAM. The ram is the finest piece of mechanistn attüched to the ship. The ram proper is 22 fev-'t of solid oak aud iron ; unhke that of the Keokuk, which protruded from the bottom of the huil near the keel, this extends from the top of the deck, being, as it were, an extensión of the entire armor of the ship. Another aavantage in this ram is, that it eould be carried away without any material damage or injury to the vessel, and without her making water. fEOïECTlNG THE ■'BOITOM. One of the greatest diflicultles in the way of making iron claus permanently useful was that of protaaling the bottoms from the filth which concentrated there and prevented them from moving. The original monitor had to be towed from Foriress Monroe to Washington on aocouut of her bottoms being so foul. The English fi igate Warrior also experienced a similar inconvenience, and we learn that some monitors at present off Charles ton are very foul. All aorts of paiuts have been tried, and all with want of success. The most popular was a sort of Enarlish "peacock'' paint, which wasused in some of the mail steamers ; but it did very little good. On the bottom of the Dictator, however, and on all of our il on-olads to be built hanceforward, and most of the naval built vessels, a successful re.uedy has been devised, which will keep the bottoms perfectly clear of all filth It is called 'iShip Ziuc" paint, and is perfectly white in color. Some thirty years since, a vessel was coated with it iu England ; she arrived here a few weeks ago, and her bottoms were found in perfect ordir. The governmeut bas responsible parties furnishiug the paint, aud jts purity eau be relied on.