 Northumberland had a two @-@ cylinder trunk steam engine , made by John Penn and Sons , driving a single propeller using steam provided by 10 rectangular fire @-@ tube boilers . It produced a total of 6 @,@ 558 indicated horsepower ( 4 @,@ 890 kW ) during the ship 's sea trials on 15 September 1868 and Northumberland had a maximum speed of 14 @.@ 1 knots ( 26 @.@ 1 km / h ; 16 @.@ 2 mph ) . The ships normally carried 750 long tons ( 760 t ) of coal , but had a maximum capacity of 1 @,@ 400 long tons ( 1 @,@ 400 t ) , enough to steam 2 @,@ 825 nautical miles ( 5 @,@ 232 km ; 3 @,@ 251 mi ) at 10 knots ( 19 km / h ; 12 mph ) . 
