Brazilian monitor Alagoas The Brazilian monitor " Alagoas " was the third ship of the river monitor s built for the Brazilian Navy during the Paraguayan War in the late 1860s . " Alagoas " participated in the Passagem de Humaitá in February 1868 and provided fire support for the army for the rest of the war . The ship was assigned to the Upper Uruguay ( ) Flotilla after the war . " Alagoas " was transferred to Rio de Janeiro in the 1890s and participated in the Fleet Revolt of 1893 – 94 . The ship was scrapped in 1900 . Design and description . The " Pará " - class monitors were designed to meet the need of the Brazilian Navy for small , shallow - draft armored ships capable of withstanding heavy fire . The monitor configuration was chosen as a turreted design did not have the same problems engaging enemy ships and fortifications as did the casemate ironclad s already in Brazilian service . The oblong gun turret sat on a circular platform that had a central pivot . It was rotated by four men via a system of gears ; 2 . 25 minutes were required for a full 360° rotation . A bronze ram was fitted to these ships as well . The hull was sheathed with Muntz metal to reduce biofouling . The ships measured long overall , with a beam of . They had a draft between of and displaced . With only of freeboard they had to be towed between Rio de Janeiro and their area of operations . Their crew numbered 43 officers and men . Propulsion . The " Pará " - class ships had two direct - acting steam engines , each driving a single propeller . Their engines were powered by two tubular boilers at a working pressure of . The engines produced a total of which gave the monitors a maximum speed of in calm waters . The ships carried enough coal for one day ' s steaming . Armament . " Alagoas " carried a single 70 - pounder Whitworth rifled muzzle loader ( RML ) in her gun turret . The 70 - pdr gun had a maximum elevation of 15° . It had a maximum range of . The 70 - pdr gun weighed and fired a shell that weighed . Most unusually the gun ' s Brazilian - designed iron carriage was designed to pivot vertically at the muzzle ; this was done to minimize the size of the gunport through which splinters and shells could enter . Armor . The hull of the " Pará " - class ships was made from three layers of wood that alternated in orientation . It was thick and was capped with a layer of peroba hardwood . The ships had a complete wrought iron waterline belt , high . It had a maximum thickness of 102 millimeters amidships , decreasing to and at the ship ' s ends . The curved deck was armored with of wrought iron . The gun turret was shaped like a rectangle with rounded corners . It was built much like the hull , but the front of the turret was protected by of armor , the sides by 102 millimeters and the rear by 76 millimeters . Its roof and the exposed portions of the platform it rested upon were protected by 12 . 7 millimeters of armor . The armored pilothouse was positioned ahead of the turret . Service . " Alagoas " was laid down at the Arsenal de Marinha da Côrte in Rio de Janeiro on 8 December 1866 , during the Paraguayan War , which saw Argentina and Brazil allied against Paraguay . She was launched on 29 October 1867 and completed in November 1867 . She arrived on the Paraná River in January 1868 , although her passage further north was barred by the Paraguayan fortifications at Humaitá . On 19 February 1868 , six Brazilian ironclads , including " Alagoas " , steamed past Humaitá at night . " Alagoas " and her two sister ships , and were lashed to the larger ironclads in case any engines were disabled by the Paraguayan guns . led with " Rio Grande " , followed by with " Alagoas " and with " Pará " . The cable tying " Alagoas " to " Bahia " was severed by Paraguayan shells and the monitor drifted down below the guns . The commander of the " Alagoas " was ordered not to attempt to pass the guns during daylight , but disregarded this order and successfully rendezvoused with the rest of the squadron upstream of the fortifications . Both " Alagoas " , which had taken an estimated 200 hits , and " Pará " had to be beached after passing the fortress to prevent them from sinking . " Alagoas " was under repair at São José do Cerrito until mid - March . Accompanied by " Tamandaré " , " Alagoas " bombarded and destroyed the Paraguayan artillery battery at Timbó , upstream of Humanitá , on 23 March . The monitor bombarded artillery positions defending the Tebicuary River in July and again in August . On 15 October she bombarded Angostura Fort , south of Asunción , in company with , , " Pará " and her sister . After the war " Alagoas " was assigned to the newly formed Alto Uruguai Flotilla , based at Itaqui . In the 1880s the ship ' s armament was reinforced with a pair of machine guns . " Alagoas " was transferred to Rio de Janeiro in the 1890s and joined the rebels in the Fleet Revolt of 1893 – 94 . Her engines had been removed by this point and she had to be towed into position to fire on the government forts . She was scrapped in 1900 .