on the sands of Dundrum Bay, Ireland. There was doubt as to whether she could be re-floated. Brunel advised that if anyone could rescue the ship then the man to do it was the naval engineer, James Bremner. He was engaged and the Great Britain was re-floated on 27 August 1847 with the assistance of HMS Birkenhead. The Birkenhead was never commissioned as a frigate, as two factors came into play while she was still under construction that resulted in her being converted into a troopship. Firstly, the Royal Navy's warships were switched from paddle wheels to more efficient propeller propulsion, following an experiment by the Admiralty in 1845 in which the benefits of the propeller over the paddle wheel were dramatically demonstrated. Secondly, the Admiralty had doubts about the effects of cannon shot against iron hulls – in a number of trials carried out at the Royal Arsenal in 1845, at lower velocities shot made a jagged hole that was hard to plug. On 15 September 1847, Birkenhead ran down and sank the brig Oratio in the English Channel off The Lizard, Cornwall. The owners of the brig sued for their loss in the Admiralty Court. Birkenhead was found to be to blame as she had no look-out posted, being nineteen short in her crew. As part of her conversion to a troopship in 1851, a forecastle and poop deck were added to the Birkenhead to increase her accommodation, and a third mast was added, to change her sail plan to a barquentine. Although she never served as a warship, she was faster and more comfortable than any of the wooden sail-driven troopships of the time, making the trip from the Cape in 37 days in October 1850. Final voyage (1852) In January 1852, under the command of Captain Robert Salmond RN, the Birkenhead left Portsmouth conveying troops from ten different regiments, including the 2nd Regiment of Foot and the 74th Regiment of Foot, to the Eighth Xhosa War against the Xhosa in the Cape Colony. On 5 January, she picked up more soldiers at Queenstown (now Cobh), Ireland, and conveyed some officers' wives and families. On 23 February 1852, Birkenhead docked briefly at Simon's Town, near Cape Town. Most of the women and children disembarked along with a number of sick soldiers. Nine cavalry horses, several bales of hay and 35 tons of coal were loaded for the