Other circumstances soon occurred which consoled the inventor for his disappointment in the rejection of the propeller by the British Admiralty. The subject had been brought to the notice of an officer of the United States navy. Captain Robert F. Stockton, who was at that time on a visit to London, and who was induced to accompany him in one of his experimental excursions on the Thames. Captain Stockton is entitled to the credit of being the first naval officer who heard, understood, and dared to act upon the suggestions of Ericsson, as to the application of the propeller to ships of war. At the first glance, he saw the important bearings of the invention; and his acute judgment enabled him at once to predict that it was destined to work a revolution in naval warfare. After making a single trip in the experimental steamboat, from London Bridge to Greenwich, he ordered the inventor to build for him forthwith two iron boats for the United States, with steam-machinery and propeller on the plan of this rejected invention. "I do not want," said Stockton, "the opinions of your scientific men; what I have seen this day satisfies me." He at once brought the subject before the Government of the United States, and caused numerous plans and models to be made, at his own expense, explaining the peculiar fitness of the invention for ships of war. So completely persuaded was he of its great importance in this aspect, and so determined that his views should be carried out, that he boldly assured the inventor that the Government of the United States would test the propeller on a large scale; and so confident was Ericsson that the perseverance and energy of Captain Stockton would sooner or later accomplish what he promised, that he at once abandoned his professional engagements in England, and came to the United States, where he fixed his residence in the city of New York. This was in the year 1839.
Circumstances delayed, for some two years, the execution of their plan. With the change of the Federal Administration, Stockton was first able to obtain a favorable hearing; and having at length received the necessary authority, the Princeton was built under his superintendence, from the designs of Ericsson. She was completed and ready for sea early in 1844, when she was pronounced by Stockton "the cheapest, fastest, and most certain ship of war in the world."
In this vessel, in addition to the propeller, Ericsson introduced his semicylindrical steam-engine, a beautiful invention, so compact that it occupied only one-eighth of the bulk of the British marine engine of corresponding power, and was placed more than four feet below the water-line. The boilers were also below the water-line, having a peculiar heating-apparatus attached which effected a great saving of fuel, and with their furnaces and flues so constructed as to burn anthracite as well as bituminous coal. Instead of the ordinary tall smoke-pipe,—an insuperable objection to a steamer as a ship of war,—he constructed a smoke-pipe upon the principle of the telescope, which could be elevated or depressed at pleasure; and in order to provide a draught independent of the height of the smoke-pipe, he placed centrifugal blowers in the bottom of the vessel, which were worked by separate small engines,—an arrangement originally applied by him to marine engines in the steam-packet Corsair in 1831. Thus the steam-machinery of the Princeton fulfilled the most important requisites for a war-steamer, combining lightness, compactness, simplicity, and efficiency, and being placed wholly out of reach of the enemy's fire.
The armament of the ship also exhibited many peculiarities. "By the application of the various arts to the purposes of war on board of the Princeton," says Captain Stockton, in his report to the Navy Department, "it is believed that the art of gunnery for sea-service has, for the first time, been reduced to something like mathematical certainty. The distance to which the guns can throw their shot at every necessary angle of elevation has been ascertained by a series of careful experiments. The distance from the ship to any object is readily ascertained with an instrument on board, contrived for that purpose, by an observation which it requires but an instant to make, and by inspection without calculation. By self-acting locks, the guns can be fired accurately at the necessary elevation,—no matter what the motion of the ship may be." The instruments here referred to, namely, the Distance-Instrument and the Self-Acting Gun-Lock, and also the wrought-iron gun-carriage, by means of which Captain Stockton's enormous guns were readily handled and directed, all were the productions of Ericsson's fertile mechanical genius.
A committee of the American Institute, by whom this remarkable vessel was examined, thus concluded their report:—"Your Committee take leave to present the Princeton as every way worthy the highest honors of the Institute. She is a sublime conception, most successfully realized,—an effort of genius skilfully executed,—a grand unique combination, honorable to the country, as creditable to all engaged upon her. Nothing in the history of mechanics surpasses the inventive genius of Captain Ericsson, unless it be the moral daring of Captain Stockton, in the adoption of so many novelties at one time." We may add that in the Princeton was exhibited the first successful application of screw-propulsion to a ship of war, and that she was the first steamship ever built with the machinery below the water-line and out of the reach of shot.
Ericsson spent the best part of two years in his labors upon the Princeton. Besides furnishing the general plan of the ship and supplying her in every department with his patented improvements, he prepared, with his own hand, the working-drawings for every part of the steam-machinery, propelling-apparatus, and steering-apparatus in detail, and superintended their whole construction and arrangement, giving careful and exact instructions as to the most minute particulars. In so doing, he was compelled to make frequent journeys from New York to Sandy Hook and Philadelphia, involving no small amount of trouble and expense. For the use of his patent rights in the engine and propeller, he had, at the suggestion of Captain Stockton, refrained from charging the usual fees, consenting to accept, as full satisfaction, whatever the Government, after testing the inventions, should see fit to pay. He never imagined, however, that his laborious services as engineer were to go unrequited, or that his numerous inventions and improvements, unconnected with the engine and propeller, were to be furnished gratuitously. Yet, when, after the Princeton, as we have seen, had been pronounced on all hands a splendid success, Ericsson presented his bill to the Navy Department,—not for the patent-fees in question, but for the bare repayment of his expenditures, and compensation for his time and labor in the service of the United States,—he was informed that his claim could not be allowed; it could not be recognized as a "legal claim." It was not denied that the services alleged had been rendered,—that the work for which compensation was asked had been done by Ericsson, and well done,—nor that the United States were in the enjoyment of the unpaid results of his labor and invention. A claim based upon such considerations might, it would seem, have been brought within the definition of a legal claim. But if not admissible under the strict rules of the Navy Department, it was certainly an equitable demand against the United States; and Ericsson could not believe that the representatives of the great American people would stand upon technicalities. He accordingly made a direct appeal to them in a Memorial to Congress.
We may as well here give the further history of this claim. It met with the usual delays and obstructions that private claims, having nothing but their intrinsic merits to support them, are compelled to encounter. It called forth the usual amount of legislative pettifogging. Session after session passed away, and still it hung between the two Houses of Congress, until the very time which had elapsed since it was first presented began to be brought up as an argument against it. At length, when Congress established the Court of Claims, a prospect opened of bringing it to a fair hearing and a final decision. It was submitted to that tribunal six years ago. The Court decided in its favor,—the three judges (Gilchrist, Scarborough, and Blackford) being unanimous in their judgment. A bill directing its payment was reported to the Senate,—and there it is still. Although favorably reported upon by two committees at different sessions, and once passed by the Senate, without a vote recorded against it, it has never yet got through both Houses of Congress. For furnishing this Government with the magnificent war-steamer which was pronounced by Captain Stockton "the cheapest, fastest, and most certain ship of war in the world," Ericsson has never been paid a dollar. It remains to be seen whether the present Congress will permit this stain upon the national good faith to continue. If it does, its "votes of thanks" are little better than a mockery.
The efficiency and utility of the propeller having been established beyond a doubt, it went at once into extensive use. But the inventor was again disappointed in his just expectation of reaping an adequate pecuniary benefit from his exertions. Upon the strength of some attempts at screw-propulsion,—made and abandoned by various experimenters,—which had never resulted, and probably never would have resulted, in any practical application, rival machines, which conflicted with Ericsson's patent, soon made their appearance. A long litigation followed, during which all attempts to collect patent-fees were necessarily suspended; and the result was, that the invention was virtually abandoned to the public. But no one can take from Ericsson the honor of having first introduced the screw-propeller into actual use, and demonstrated its value,—an honor which is now freely accorded to him by the highest scientific authorities at home and abroad.
Although the first five years of his American experience had been less profitable, in a pecuniary sense, than he had anticipated, he continued to reside in the city of New York, where he found an ample field for the exercise of his great powers in the line of his profession. He planned the war-steamer Pomone, the first screw-vessel introduced into the French navy. He planned revenue-cutters for the United States Government, taking care always to have his contracts so distinctly made that no question could again arise as to his "legal claim." He invented a useful apparatus for supplying the boilers of sea-going steamers with fresh water. He invented various modifications of the steam-engine.
In the American division of the London Industrial Exhibition of all Nations in 1851, he exhibited the Distance-Instrument, for measuring distances at sea,—the Hydrostatic Gauge, for measuring the volume of fluids under pressure,—the Reciprocating Fluid-Metre, for measuring the quantity of water which passes through pipes during definite periods,—the Alarm-Barometer,—the Pyrometer, intended as a standard measure of temperature, from the freezing-point of water up to the melting-point of iron,—a Rotary Fluid-Metre, the principle of which is the measurement of fluids by the velocity with which they pass through apertures of different dimensions,—and a Sea-Lead, contrived for taking soundings at sea without rounding the vessel to the wind, and independently of the length of the lead-line. For these inventions he received the prize-medal of the Exhibition.