Summary

Frank Coffee Forty Years On The Pacific — Oil and Fuel Used at Sea (1920)

A ship of, say, eight or ten thousand tons, making fourteen knots an hour, could often in fair weather do fifteen knots, but that extra mile an hour would probably cost in coal or oil consumption, $150 or $200 more in the twenty-four hours. Oil makes very little smoke when intelligently "fired." If you want to make a chief-engineer of an oil-burner jump, point out the volume of black smoke coming out of the steamer's smokestacks. He will make for the fire-room and raise Cain. A big volume of smoke shows waste of oil and bad combustion.
Source: Wikisource

Frank Coffee Forty Years On The Pacific — Oil and Fuel Used at Sea (1920)

Again, bad time is often attributed to poor coal.
The human element is also to be reckoned with. Firemen get very thirsty and go ashore at way ports, where they may drink too much. This prevents a ship sailing at the advertised time, and so well is the Firemen's Union organized, that it will hold up a ship and not let her go until the last fireman is on board.
Source: Wikisource

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