The steamship Atlantic, A. G Gray, Esq. cornmanding, lelt New York on Sunday, April 7, iwader sealed ordew irom the government. At 8 A. M. discharged pilot, and at 10 A. M. shaped her oourse iu compliance with orders. On Monday, tho 8th, at 4 F. M., the wind Buddenly shiittnl and b'ow fresh irom southeaet, and ko continued untiï midnght, whon t was increased to a heavy gale. ín order to save the borses tho ship was hove to with her head to southoast. Alter the gale had abated we proceeded on our course for Key West, havïcig laid to for 36 houra. We arriVed and dropped anchor in the ouLer roads at Key West, tbree miles from Fort Taylor, at 2 P. M, on Saturday, tho 13th, when one oí our boats was sent to Fort Taylor, oen wring Col. Brown and hiaetafl, wha had a proloDgèd interview with tho United States otficers, both military and civil, At 7 P. M. commenced receiving additional troops, ordnanee, ordnance S shells, &c, &c , wbich were placed on a lighter and towed out to tho Atlantic by the United States etearner Orusader, Capt. Uraven. This labor Was continued without cessation nntil 4 A. M. of Sunday, ihe 14th, and at 6 A M. we weighed anchor and Bteered f r Tortugas, where we anchoi ed close to Fort Jefléraón at 2 P. M. same day. At this pomt we to(k on board more otfieers, troop?, laborera, howitzora, gun carriages, materials, &c, and at U P. M. were uodar way for our final d stination, which namnv known onty to Col. Brqwo and Capt. Meig8 of the arrny, and to Capí. Uray of the Atlantic. Diuing tho uight and the ru'xt day graat curiosity was munifefeted, and akhough the sliip's court-u seomed to indícate Fort Pickon, vet it was not until the evening ol MoutJay, the 15tb,thatthe secret was dwcloeed and the rciniorcement of Fort Piekens openly announeed. Op to this time all waa conjecture; but now the countenances of all on board beauied with the kbowledge of an approaching event Activity and preparation took the place of supinenesa and unewtainty, and the faet that Fort Piekens cuuld be and would bo reinforced was settlad thal night. On Tucsday, the IGih, at 6J P. M., we anchored ofl' Santa llosa I (Fort Piekens being on it western extremity), tour miles Irom snore, cl se by the frigate Sabino, tho flag ship of the squadron, Oom, Adams. After comraunicating with the Commander and the naval Captains present, we look in tow the boats of the fleet, some twenty iu number, and alter dark weighed anchor and fctóod in'ehore, all lights being extiaguished, and carne to anchor within a mile ot Fort Pickens, and in direct range of tho guna of Fort MeRae and the water-batteries, and tbree quarters oí' a mile from the beach, ia four l'üthoms of water. At 'J tho first boat pushed bfl for the beacb,"with Col. Browa and Capt. Meigs, who were the first to surprise the intivpid Slemmor nnd his command. During the erabarkatioD of tho troopa is ibè boata, the signal from Fort Pixikensfor an Bpprehended attack was mm!e by the sending up of roefceta - This signal was repeated, and bastaned the oporations. Capt. Vodges and other officers in the fort were aetoeiahed at therapidity of the reinloreernent, JJel'ore midnight the majority of the officers and soldiers were sáfcly ín the fort, and, although a heavy surf was running diiriiigthfl oigh.r, no accident (1 nny bind oócrii r í'hia sucoessful latitling took place three-uays after the botnbai dment and aurrepder of Fort Sumptcr, a fact well knnwn on the main 'and, but not known at Fort Pickens, nor by the forcea aftoat. Early iii the morning ot' the ITih, the ' remaining troops were landed, excepting j the artülery-mea of Cvptain Barry's '■■ compan ■, -, o remained to land with their horses. At, 8 A. M. we again weiffhed anchor and stood to the castward, and anchored about 3J miles from Fort Pickens and half a mile from tha boach. This petint wis Beleefed as the best placo for landing the horses. This diiïïcult work was commenoed in 1he afternoon, continued during tho night, oud ilui.shcd on the morning of the 18ïh. The United States steam frigato Pow: hattan, èomm'anded by Capt. David D. Porter, arrived oa the afternoon of t!ic 17 th, and after coinmuniéating with tbe i'lag-ship, took position just ahcad of aSl in order to cover tbc future landing. In this movoment sho was followed by tho Broóklyn, Capt. Pöor, vrhicH anchored under our stern. The Wyandotte was ! ng ubout ; the Sabine, St. Louis and ' supply being outside about threc miles distant. Tho boats of all the ships of1 the Squadron were actlvely engaged in ! landing troops and store?, &?., from the ; Dight of the IGth untü the morning of the i:jd. Tho Illinois, with reinforcearrlved al midnight on tho lüth, p.ml her troops were lanclod tho next morn: Sevcu of the horses wcro lost - föiir diod on the passage, one was drowned alongside, ono had hia ueck broke in the serf, acd one died from exhatistion on reaehing tho shore. The fornge a:id light nrtillsry were landcd siinultaneously with the horses. On tho 18th the landing of tho general cargo of; heavy and light ordnance, ammuuition, ' provisión, &c., &o , were i'airly j nienced and continuad, with but pirtial nterruption, until tho forenoon of ïnesday, -'.k, when it was final ly dtscharged, to tho great gratiñeation oí' all j ed Theposition of the Pvvohatan and j lyn was Buch that thi Santa Llosa Islam! aud prevent a lanrjing from the main hun!, and at tho sanie tune shielJ the huil of the Atlantic. At no timo was our steain allowed to go down, so that in case of uttack, or galo, or any . uu-y, wo wcro rcady togo offshore. On Monday, Col. Browu, tiio coturoander of the United Statea in Florida, gave I i". Port L'iukens, the ary certificóte atfd 1 dis■:■ Key West. Ou Tuesday, (Japt. Meigs, tho indefatigable Engïneer of tho expedition oame ou bdard and at noon we wero passing through thd saluting aud saluted, ■ iy to Key al. We arrived at Key West at ü A. M. of tho 25th, makicg tno run in tbrtv-two hours. We wore here dis oai, as M r. Tift, the only private owner ofceal, refused to f-cll coal to this or s, ■;■ cm■ ! ii', the governiaent, he boin course, a secessionist. Ah tho Mohawk and Crusader wero aliead of us to eoal at an government wharf, and to liavc waitcd tli e ld have caused grcat dolay, wc weigh ( (I anohor, and at 11 A. M. paased Band Koy liglit, and at sundown passed Moro Castlo and info Havana Iiarbor, makiug tliR run across in 1 bour. Haring coinpleted coaüngat 11:15 A. M., Saturday, 27th, we got under way, and at twonly minutes past noon wc pas' sed the Moro and ghaped our coursc for New York) and aftcr a pleasant passagu arrived oü' Sandy Hook on Wcdncsday moruirig, maling the trip in throo day and cigliteon and onc-halt' hours.