Two innovations in shipbuilding were soon introduced. These were the building of iron instead of wooden ships and the replacing of the paddle wheel by the screw propeller. The screw-propeller was first successfully introduced by the famous Swede, John Ericsson, in 1835. His propeller was tried in a small vessel, forty-five feet long and eight wide, which was driven at the rate of ten miles an hour, and towed a large packet ship at fair speed. Ericsson, not being appreciated in England, came to America to experiment. Other inventors were also at work in the same line. Their experiments attracted the attention of Isambard Brunel, one of the greatest engineers of the period, who was then engaged in building a large paddle-wheel steamer, the Great Britain. Appreciating the new idea, he had the engines of the new ship changed and a screw propeller introduced. This ship, a great one for the time, 322 feet long and of 3443 tons, made her first voyage from Liverpool to New York in 1845, her average speed being 12 1/4 knots an hour, the length of the voyage 14 days and 21 hours. By the date named the crossing of the Atlantic by steamships had become a common event. In 1840 the British and Royal Mail Steam Packet Company was organized, its chief promoter being Samuel Cunard, of Halifax, Nova Scotia, whose name has long been attached to this famous line. The first fleet of the Cunard Line comprised four vessels, the Britannia, Acadia, Caledonia and Columbia. The Unicorn, sent out by this company as a pioneer, entered Boston harbor on June 2, 1840, being the first steamship from Europe to reach that port. Regular trips began with the Britannia, which left Liverpool on July 4, 1840. For a number of years later this line enjoyed a practical monopoly of the steam carrying trade between England and the United States. Then other companies came into the field, chief among them being the Collins Line, started in 1849, and of short duration, and the Inman Line, instituted in 1850. We should say something here of the comforts and conveniences provided for the passengers on these early lines. They differed strikingly from those on the leviathans of recent travel and were little, if any, superior to those on the packet ships, the active rivals at that date of the steamers. Then there were none of the comfortable smoking rooms, well-filled libraries, drawing rooms, electric lights, and other modern improvements. The saloons and staterooms were in the extreme after part of the vessel, but the stateroom of that day was little more than a closet, with two berths, one above the other, and very little standing room between these and the wall. By paying nearly double fare a passenger might secure a room for himself, but the room given him did not compare well even with that of small and unpretentious modern steamers.