In following the progress of the screw, as applicable to the propulsion of merchant vessels,(32) and its use in other countries, we must now recur to the period when Ericsson was making his experiments on the Thames. At that time an intelligent gentleman, Captain Robert F. Stockton, of the United States’ Navy, was on a visit to London; being of an inquisitive turn of mind, like most of his countrymen, he watched with great interest the trials with the screw then in progress, and having obtained an introduction to Ericsson, he accompanied him on one of his experimental expeditions on the Thames. Unlike the Lords of the British Admiralty, who allowed eight years to elapse before they built their first screw-propeller, the _Rattler_, Captain Stockton was so impressed with the value and utility of the discovery, that, although he had only made a single trip in the _Francis B. Ogden_, and that merely from London Bridge to Greenwich, he there and then gave Ericsson a commission to build for him two boats for the United States, with steam machinery and propeller as proposed by him. Stockton, impressed with its practical utility for war purposes, was undismayed by the recorded opinions of scientific men, and formed his own judgment from what he himself witnessed. He, therefore, not only ordered the two iron boats on his own account, but at once brought the subject before the Government of the United States, and caused various plans and models to be made at his own expense, explaining the fitness of the new invention for ships of war. So sanguine was he, indeed, of the great importance of this new mode of propulsion, and so determined that his views should be carried out, that he encouraged Ericsson to believe that the Government of the United States would test his propeller on a large scale; Ericsson, relying upon these promises, abandoned his professional engagements in England, and took his departure for the United States. But it was not until a change in the Federal administration, two years afterwards, that Captain Stockton was able to obtain a favourable hearing. Orders were then given to make an experiment in the _Princeton_, which was successful. The propeller, as applied to this war vessel, was similar in construction to that of the _Francis B. Ogden_, as well in theory as in minute practical details. One of the boats, named after her owner, the _Robert F. Stockton_, was built by Messrs. Laird, of Birkenhead, and launched in 1838. She was 70 feet in length, 10 feet wide, and drew 6 feet 9 inches of water. Her cylinders were 16 inches diameter with 18 inches stroke, and her propellers 6 feet 4 inches in length. On her trial trip on the Thames, made in January of the following year, she accomplished a distance of nine miles in about half an hour with the tide, proving the speed through the water to be between eleven and twelve miles an hour. On her second trial, between Southwark and Waterloo Bridges, she