In his splendid book “Transatlantic,” Stephen Fox offers a definitive history of commercial navigation across the North Atlantic Ocean, from the introduction of steam power in the 1820s to the early years of the 20th century.

In the early 1800s, sailing ships were the standard for trans-Atlantic travel. Called “packet” ships, they sailed mostly on New York-to-Liverpool, England, and Boston-to-London routes, departing “to sail from each port on a certain day of every month throughout the year,” according to a newspaper ad from 1817.

Europe-bound crossings took at least three weeks, and the return trip, made against currents and winds, was twice as long. The ships sailed through violent, storm-prone waters, sometimes in cold weather and dense, persistent fog, and, in certain seasons, through fields of icebergs that drifted from the North Pole.

Ocean crossings were uncomfortable, to say the least. Passengers’ desire for faster crossings on regular schedules was among the factors that brought about the use of steam to power ships.

The first regular steamship service between England and America began on July 4, 1840, when the wood-hulled paddle-wheeler Britannia left Liverpool for Halifax, Nova Scotia, and Boston. The ship belonged to the new Cunard Line, whose founder, Samuel Cunard, was aboard for the crossing. The Britannia arrived in Boston two weeks later, in about one-third the time of a packet ship.

Fox details the many far-flung efforts that had been made in England, Scotland and America to use steam to propel ships. In America, paddle-wheelers were developed for use on rivers and lakes; in England and Scotland, a growing number of engineers aimed at building bigger, heavier seagoing ships.

Thus, in the initial stages of the steamship era, England was pre-eminent in trans-Atlantic navigation, and pre-eminent among the English shipping companies was the Cunard Line.

Cunard long dominated the trans-Atlantic steamship field, competing successfully against the Collins, Inman, White Star, Guion, Hamburg-Amerika and North German Lloyd lines. Fox has done a magnificent job chronicling the histories of these lines and their ships, and of their passengers, many of whom have left written accounts.