sections. Propulsion: steam and sail The first ocean-going ironclads carried masts and sails like their wooden predecessors, and these features were only gradually abandoned. Early steam engines were inefficient; the wooden steam fleet of the Royal Navy could only carry "5 to 9 days coal", and the situation was similar with the early ironclads. Warrior also illustrates two design features which aided hybrid propulsion; she had retractable screws to reduce drag while under sail (though in practice the steam engine was run at a low throttle), and a telescopic funnel which could be folded down to the deck level. Ships designed for coastal warfare, like the floating batteries of the Crimea, or and her sisters, dispensed with masts from the beginning. The British , started in 1869, was the first large, ocean-going ironclad to dispense with masts. Her principal role was for combat in the English Channel and other European waters; while her coal supplies gave her enough range to cross the Atlantic, she would have had little endurance on the other side of the ocean. The Devastation and the similar ships commissioned by the British and Russian navies in the 1870s were the exception rather than the rule. Most ironclads of the 1870s retained masts, and only the Italian navy, which during that decade was focused on short-range operations in the Adriatic, built consistently mastless ironclads. During the 1860s, steam engines improved with the adoption of double-expansion steam engines, which used 30–40% less coal than earlier models. The Royal Navy decided to switch to the double-expansion engine in 1871, and by 1875 they were widespread. However, this development alone was not enough to herald the end of the mast. Whether this was due to a conservative desire to retain sails, or was a rational response to the operational and strategic situation, is a matter of debate. A steam-only fleet would require a network of coaling stations worldwide, which would need to be fortified at great expense to stop them falling into enemy hands. Just as significantly, because of unsolved problems with the technology of the boilers which provided steam for the engines, the performance of double-expansion engines was rarely as good in practice as it was in theory. During the 1870s the distinction grew between 'first-class ironclads' or 'battleships' on the one hand, and 'cruising ironclads' designed for long-range work on the other. The demands on first-class ironclads for