Herval was an iron-hulled, fully rigged central battery ship. It was 191feet long. The ship had a beam of 36feet and a maximum draft of 9feet. Herval displaced 1353MT. Its crew consisted of 125 men. The engines produced a total of 600ihp and gave Herval a maximum speed of 9kn. Herval was armed with four 70-pounder Whitworth rifled muzzle-loading guns. The ship was protected by a 4.5inches iron belt and at the casemate.
Herval was built at the shipyards in Plymouth, England. It was the second ship to bear the name Herval, in honor of general Manuel Luís Osório, Marquis of Erval. The ship was originally ordered by Paraguay, who named it Medusa, but it was sold to Brazil as the Paraguayans, in financial difficulties due to the ongoing Paraguayan War, were unable to pay for it. It belongs to the same class as the armored corvette Mariz e Barros. The ship arrived in Brazil on 30 May 1866 and on 19 July of the same year it was officially named Herval, being incorporated into the navy also in the same year under the command of first lieutenant Tomás Pedro de Bittencourt Cotrim.[1]
Its main actions took place during the Paraguayan War. On 2 February 1867, Herval participated in the bombing of Curupayty. On 2 March 1868, together with the ironclad Brasil, it went to the aid of the ironclads Lima Barros and Cabral, repelling a Paraguayan attempt to board the ships. Also in 1868, it took part in operations in Curupayty, Humaitá and Angostura.
After the war, it underwent renovation in 1875 in Rio de Janeiro. It was decommissioned in 1879, with its machines being removed to be used in the corvette Primeiro de Março.