This image is of HMS Donegal (right front) and in the background HMS Sans Pareil (centre) and an unknown gunboat (left).
HMS Donegal was a 101-gun screw-driven ship of the line launched at Devonport Dockyard in 1858.
She initially joined the Channel Squadron, took part in several fleet reviews and in 1861 transported troops to Mexico. She also spent several years as a coastguard vessel at Liverpool and famously took the last surrender of the American Civil War when on 6 November 1865 the CSS Shenandoah surrendered after travelling from the Pacific Ocean where news of the end of the Civil War had reached her.
Donegal then became flagship of Vice-Admiral Sir Henry Kellett on the China Station before becoming a tender to HMS Duke of Wellington, which was then in Portsmouth as receiving ship
She was was paid off in 1870 and was hulked in 1886 becoming part of the Torpedo School at Portsmouth, when her name was changed to Vernon.
HMS Sans Pareil was a 70-gun screw propelled ship of the line launched in 1851. She served with the Channel Fleet and at the outbreak of the Crimean War was reassigned to the Black Sea. She was in China during the Second Opium War and, like Donegal was used to transport troops to Mexico in 1861. It is therefore possible that it was during this deployment that the image was taken.