Soon after this successful voyage, the Hudson boat was advertised and established as a regular passage-boat between New York and Albany. She, however, in the course of the season, met with several accidents, from the hostility of those engaged in the ordinary navigation of the river, and from defects in her machinery, the greatest of which was having her water-wheel shafts of cast-iron, which was insufficient to sustain the great power applied to them. The wheels also were hung without any support for the outward end of the shaft, which is now supplied by what are called the wheel-guards. At the session of 1808 a law was passed to prolong the time of the exclusive right to thirty years; it also declared combinations to destroy the boat, or wilful attempts to injure her, public offences, punishable by fine and imprisonment. Notwithstanding her misfortunes, the boat continued to run as a packet, always loaded with passengers, for the remainder of the summer. In the course of the ensuing winter she was enlarged, and in the spring of 1808 she again began running as a packet-boat, and continued it through the season. Several other boats were soon built for the Hudson River, and also for steamboat companies formed in different parts of the United States. On February 11, 1809, Fulton took out a patent for his inventions in navigation by steam, and on February 9, 1811, he obtained a second patent for some improvements in his boats and machinery. About the year 1812 two steam ferry-boats were built under the direction of Fulton for crossing the Hudson River, and one of the same description for the East River. These boats were what are called twin-boats, each of them being two complete hulls united by a deck or bridge. They were sharp at both ends, and moved equally well with either end foremost, so that they crossed and recrossed without losing any time by turning about. He contrived, with great ingenuity, floating docks for the reception of these boats, and a means by which they were brought to them without a shock. These boats, were the first of a fleet which has since carried hundreds of millions of passengers to and from New York. From the time the first boat was put in motion till the death of Fulton, the art of navigating by steam advanced rapidly to that perfection of which he believed it capable; the boats performed each successive trip with increased speed, and every year improvements were made. The last boat built by Fulton was invariably the best, the most convenient, and the swiftest.