Iron paddle steamer Ajax, built Thomas Vernon & Co., Liverpool 1846
846 grt, 591 nrt, 206.4 x 27.5 ft. 3 masts
Engines by Bury and Curtis, Liverpool, 325hp.
Owned Cork Steam-ship Company.
Voyage London to Cork via Southampton, Plymouth and Falmouth.
In fine weather, on 13 October 1854, struck rock near the Mewstone and sank.
Captain Rochford, crew and about 350 passengers all saved.
For wreck now see here.

From Illustrated London News - Saturday 7 February 1846
  A DOUBLE LAUNCH AT LIVERPOOL. The animated and unusual spectacle of the launch, at the same time, of two splendid first-class iron steamers, took place on Wednesday week, at the ship-building works of Messrs. Vernon and Co., Sefton-street, Liverpool. The dimensions of these two fine vessels are, as near as possible, the same: their burden, 763 tons; length between perpendiculars, 200 feet; depth, 17.5 feet; beam, 28 feet; and their engines of 325 horse power. The Windsor, which is to ply between Liverpool and Belfast, is clinker built, and has very fine lines; her engines are constructed on the side lever principle. The Ajax, for the London and Cork trade, is carvel built, and not so fine, with direct levers. About half-past ten o'clock, it then being nearly high tide, and all the preparations being perfected, Mrs. Grantham christened the Windsor, and Mrs. Hazleden the Ajax; the ceremony being hailed by the cheers of all present; and the stages being knocked away, the two noble vessels, one after the other, glided gracefully and majestically into the river, amid the reiterated plaudits of the spectators.

Image (from Illustrated London News) of launch of Ajax and Windsor at Liverpool:

From Dublin Evening Mail - Wednesday 18 October 1854
  LOSS OF THE CORK STEAMER AJAX. The wreck of the Ajax, near the Mewstone, in the English Channel, is one of the most remarkable that has occurred for many years. The Ajax left London on her voyage for Southampton, Plymouth, Falmouth, and Cork, on Wednesday, with about 350 passengers, and a general cargo worth about £30,000. The weather was fine, and she had a splendid passage, until about half-past four on Friday afternoon, when she was in sight of Plymouth Sound. The weather was still fine and clear, and the water still and calm. The vessel was forging away with her accustomed power. The captain (Rochford), having dined, had been on the bridge about half an hour, directing the course of the vessel. The second mate, thinking that sufficient distance had not been given to the Mewstone, ventured to suggest the same to the captain, but was asked if he (the captain) did not know how to navigate the English Channel?
  Very shortly afterwards the vessel struck on one of the rocks lying off the south east of the Mewstone. The shock was rather gradual, but sufficient to rouse the fears of the whole of the persons on board. The vessel had run on a pointed rock, the apex of which had entered her hull. The captain, alive now to the danger, gave the word to stop the engines. This was done, and in another moment he called upon the engineer reverse the engines; but the engineer having by this time ascertained the state of affairs, that there were four feet of water in the hold, and remembering the fate of the Victoria, refused to obey, believing that the result would be the sinking of the vessel, and perhaps the loss of many lives, and in this a few moments served to show was right. The water was pouring in so fast that had she been got off the rock, nothing could have prevented her from going down, in all probability before the passengers could have been got off.
  The boats were then launched, and, very shortly, boats arrived from her Majesty's ship Calcutta, and from ships in the Sound, and the whole of the passengers, crew, and officers, got into them, and were landed on the Mewstone, about a quarter of a mile distant. The sad misfortune was observed by the look-out men at the government stations, and reported to the Admiral, who ordered the Confiance steam tug to proceed with all possible speed to render assistance. The Dublin Company's steam vessel, the City of Limerick, then at Milbay Pier, and a large boat from the Preussischer Adler steamer, also went to render any assistance that could be afforded. Mr. Thomas Nicholson, the company's agent at Plymouth, was on board soon after the unfortunate event, and was indefatigable in his endeavours to provide for the safety of the passengers, as well as for that of the ship. Immediately the vessel struck, the water rushed in with considerable force, and with such rapidity, that even the passengers who were below at the time were unable to secure any of their luggage; and many of the poor Irish deck passengers were landed almost in a state of nudity, as in the scramble to get away they lost even the clothes from their backs. In the course of the evening and night, many boxes of clothes and goods were picked up.
  The confusion and distress of the passengers, most of whom were poor Irish, were very great. On arriving at Milbay Pier, two women were found prematurely in labour, and in the small office of the Pier-master, Captain Martin, which was kindly given up to the poor women, the accouchements took place, happily without any apparent ill effects to either the mothers or the infants. - When it became known that the vessel had struck and was filling, one poor old woman, aged upwards of seventy, threw off her clothes and jumped overboard, but was quickly taken up by one of the boats around. A soldier (insane) also took off his clothes and jumped overboard; he was taken up, but his whereabouts was unknown for some time. A young woman, who had gone down into the hold for slumber, was taken out with some difficulty.
  On Saturday morning it was found that the Ajax had broken in two, and that but a small portion of her was visible. The boats and steamers on the look-out picked up many boxes of apparel, bundles of clothes, and some light goods, including many large boxes of lucifer matches, which of course were all spoiled. The Ajax belonged to the Cork Steam-ship Company, was a very fine, powerful vessel, and a favourite with all passengers on tne line. She was built at Liverpool eight or ten years since, was 800 tons register, and 400-horse power.
  She has for years been commanded by Captain Tooker, and never had mischance before. Prior to leaving Cork for this voyage, Captain Tooker, being unwell, sought and obtained leave of absence, and Captain Rochford, who had been in the Company's service, was appointed to the command in the absence of Captain Tooker. It is somewhat singular that the same Capt. Rochford lost the Minerva, a steamer belonging to the same company, in the Irish Channel, about three weeks since - no recommendation, we should imagine, for his employment in the English Channel, and to be entrusted with much valuable property, and with the lives of so many persons. Captain Rochford left Plymouth by railway, on Saturday, for Liverpool, it was said.
  The Ajax had at the time of the accident 350 passengers, of whom sixty were government emigrants for Australia, who were being brought to the Plymouth depot for embarkation in the Samuel Boddington; ten soldiers belonging to various regiments, some recruits, and one gentleman, a youth, and a German lady, cabin passengers. All the rest were labouring Irish for Cork, three-fourths or more being women and children. On Sunday morning the starboard paddle box was above water, and the wreck still held together. The boats and steamers had not succeeded in laying hold of but a small portion of her cargo. Amongst the shippers whose goods are lost are Mr. Lonsdale, Messrs. Holman and Pardue, Mr. Richards, and other drapers of Plymouth and Devonport, and Mr. Best and several grocers; but the bulk of the cargo was for Cork, including 500 chests of tea. The bows of the vessel have disappeared, but the afterpart yet holds together, so that nothing has yet left the hold. A store was fitted up with straw for the accommodation of the passengers: it is supposed that they will be sent to Bristol or Dublin to be conveyed to Cork. The next of the Cork Company's vessels for Cork from this port leaves Saturday next. Had there been as much surf or motion of the water on Friday as there has been since, many lives would have been lost, as it would have been impossible for boats to come alongside. Daily News.

From Shipping and Mercantile Gazette - Tuesday 31 October 1854
  Wreck of the Ajax steamer off Plymouth
  The last remnant of this once noble vessel has now totally disappeared. On Thursday morning a diver went out to the wreck, for (strange to say) the first time, for she was on the rocks from the previous Friday, and the weather during the whole of that time was beautifully fine; but the diver did no good, notwithstanding his visit and his dive.
  He found the whole of the afterpart of the vessel whole and sound, as well as the engines, but the forepart, from the mainmast forward, had parted and sunk into deep water; the afterpart, including the aft-hold, had fallen over on the larboard side, that is out to sea on the rock, and this portion was then full of water at low water.
  Captain Tooker who had had the command of the Ajax for several years, up to the last voyage to London, having heard of the calamity at Cork, came to Plymouth, and went out with a diver to the wreck, and showed him where to go down. He did go down into the state cabin, but while there the tube which supplied him with air had got entangled, and he was obliged to come up; had he gone down straight into the afterhold this could not have happened, and he might have sent up some valuable property. He came ashore and brought nothing, though he saw property of every description floating all around him.