 In the 18th and early 19th centuries fleets had relied on two types of major warship , the ship of the line and the frigate . The first major change to these types was the introduction of steam power for propulsion . While <unk> steamer warships had been used from the 1830s onwards , steam propulsion only became suitable for major warships after the adoption of the screw propeller in the 1840s . 
