On 21 September 1835 Peacock was confirmed as master of the Medea steamer in the Mediterranean, and, while serving on the coast of Greece, made a survey of the isthmus of Corinth, marking the line of a possible canal.

In 1840 he applied to be appointed to the Blenheim, then going to China; his application was refused, and, being offered the command of the steamers of the newly constituted Pacific Steam Navigation Company, he resigned his warrant in the navy.

For the next five years he acted as the company's marine superintendent, and claimed to have during this time laid down buoys, erected beacons, built a lighthouse, surveyed harbours, opened and worked coal-mines, discovered new guano-beds, suggested railways, and brought the first regular mails from Valparaiso to Panama.

In 1846 he returned to England, and seems to have been busy for the next two years in carrying out experiments with an anti-fouling composition for the bottoms of iron ships, for the manufacture of which he started a company in 1848, under the style of Peacock & Buchan.

He printed the memorial, letters, and certificates, under the title of ‘Official Correspondence.’ In 1860 he commanded an unsuccessful expedition, under the patronage of Napoleon III, for the discovery of ‘nitrates’ in the Sahara, the idea being, apparently, that they were the natural concomitants of sandy desert.

8vo, 1878); ‘Notes on the Isthmus of Panama and Darien;’ ‘The Guinea, or Gold Coast of Africa, the veritable Ophir of Scripture.’ He died on 6 June 1883, in the house of his son-in-law, Henry Cookson of Liverpool, and was buried at Starcross.