But, after looking at the nearest parallel in the facts of history, each of us may make his own guess.

The airship appears now to be much farther advanced than the steamboat was for many years after Robert Fulton died.
Already we have seen men ride the wind above the sea from the New World to the Old.

Already United States mails are regularly carried through the air from the Atlantic to the Golden Gate.

It was twelve years after the birth of Fulton's Clermont, and four years after the inventor's death, before any vessel tried to cross the Atlantic under steam.

This was in 1819, when the sailing packet Savannah, equipped with a ninety horsepower horizontal engine and paddle-wheels, crossed from Savannah to Liverpool in twenty-five days, during eighteen of which she used steam power.