 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 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 <a href='uninflect' title='1'><mark>were</mark></a> widespread . However , this development alone <a href='negative_concord' title='2'><mark>was</mark></a> <a href='negative_concord' title='3'><mark>not</mark></a>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 , <a href='drop_aux' title='4'><mark>is</mark></a>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 1860s , steam engines improved with the adoption of double @-@ expansion steam engines , which used 30 – 40 % less coal than earlier models . da Royal Navy decided to switch to the double @-@ expansion engine in 1871 , and by 1875 they was widespread . However , this development alone ain't enough to herald the end of tdamast . Whether this was due to a conservative desire to retain sails , or was a rational response to the operational and strategic situation , a matter of debate . A steam @-@ only fleet would require a network of coaling stations worldwide , which would gotta be fortified at great expense to stop em fallin into enemy hands . jus as significantly , because of unsolved problems with the technology of thdaoilers which provided steam fir the engines , the performance of double @-@ expansion engines was rarely as gud in practice as it was in theory .