The value of the steam-engine having now been fully established as a means of propelling vessels at sea with safety, and of performing voyages with a regularity hitherto unknown, Mr. Napier found comparatively little difficulty in inducing capitalists to join him in the project of constructing various vessels for a regular line of steam traffic between Liverpool, Greenock, and the city of Glasgow. Three vessels were, consequently, built—the _Robert Burns_ of 150 tons, the _Eclipse_ of 240 tons, each being fitted with two engines of 30 horse-power, and the _Superb_, also of 240 tons with two engines of 35 horse-power each. These vessels proved successful, and the line thus established in 1822 has continued ever since. New coasting lines soon followed, and, in lieu of the Leith smacks, once so celebrated, the _James Watt_ was constructed to ply between London and Leith. She was the largest steamer that had yet been built, being 448 tons measurement, fitted with engines of 50 horse-power each, by Boulton and Watt. Her paddles were moved, not directly by the engines, but, through the interposition of toothed wheels, rendering the number of revolutions of the axis considerably greater than that of the paddles, so that, with the exception of the low proportion of her propelling power to the tonnage, she possessed many, if not most, of the qualities of the steamers of even the present day. The _Soho_ followed the _James Watt_ on the same line, and proved equally successful. [Sidenote: The _United Kingdom_, 1826.] In 1826 the first of the so-called leviathan class of steamers, the _United Kingdom_ (of which the following is an excellent illustration) was built by Mr. Steele of Greenock for the trade between London and Edinburgh. She was 160 feet long, with 26½ feet beam, and engines of 200 horse-power by David Napier, and was considered the wonder of the day. People flocked from all quarters to inspect and admire her.[109] [Illustration: THE “UNITED KINGDOM,” LONDON AND EDINBURGH PACKET.— FROM A DRAWING BY E. W. COOKE, R.A.] Although these two lines of regular steam communication between Liverpool and the river Clyde, and between London and Edinburgh were now successfully established, and proved of considerable importance in the encouragement of steam navigation elsewhere, some years elapsed before those rapid strides were made in its adaptation as a propelling power which have rendered it one of the wonders of the present age. Indeed, this power would probably never have made such an extraordinary advance had iron not been adopted instead of wood for the construction of our ships. [Sidenote: First idea of iron ships, 1830.]