The first steamboat constructed and used for serviceable purposes in Great Britain was the Comet, built by Henry Bell, on the Clyde, in 1812. She was only 40 feet long, 10 feet broad, of 24 tons measurement; her engines were of 4 nominal horse-power, and of very curious design, as shown by the engraving on page 70; her speed under favorable conditions was only 5 miles an hour. She continued to ply for some years between Glasgow and Greenock, and was doubtless a very great convenience to the public at that time; but the advance that has been made in the construction of river steamers for service on the Clyde and its estuary is seen by reference to the illustration of the steamer Duchess of Hamilton, whose dimensions are length, 250 feet; breadth, 30 feet; and depth 10 feet; her engines having cylinders 34-1/2 inches and 60 inches diameter, with a piston-stroke of 5 feet. Her speed is over 18 knots, or very nearly 21 miles per hour, at which rate she was going when the photograph was taken. [Illustration: Passenger Steamer Duchess of Hamilton at Full Speed—21 miles per hour. (Built for service on the Clyde.)] The paddle steamer Puritan is another example of the very great progress made since the days of the Clermont, and is also a marked advance in many ways on the Bristol, which was the wonder of a few years ago; and another noted case is the steamship Columba, built for service on the Clyde. The first steamships to cross the Atlantic from England were the Sirius and Great Western,[13] names never to be forgotten. The Great Western was built at Bristol, England, and completed in the year 1838. She was 212 feet long, 35 feet 4 inches broad, and 1,340 tons burden, and had engines of 450 nominal horse-power. She did the voyage from Bristol to New York in 15 days. The time of her quickest passage, given in the table on page 80 as 10 days, 10 hours, and 15 minutes, is not the actual passage, but is the equivalent of a passage reckoned from Queenstown to Sandy Hook. [Illustration: Passenger Steamer Columba at Full Speed—21 miles per hour. (Built for Clyde passenger service.)] In 1840 the Britannia, the first of the Cunard steamers, was put on her station. She was a paddle boat, built of wood, and was 207 feet long. Her speed on service was about eight and a half knots, so that she did the passage in 15 days. Ten years later the now renowned Inman Line commenced with an iron screw steamer named the City of Glasgow, of 1,600 tons burden, and 350 nominal horse-power, a new departure in both ship and propeller. It was not until 1855 that the Cunard Company built an iron steamer, and they continued to employ paddle boats until 1862, when the celebrated steamship Scotia was completed. It is interesting to note, in passing, that the average length of voyage in the Cunard Line, in 1856, from Liverpool to New York was 12.676 days, and from New York to Liverpool 11.036 days.