Keenly as Ericsson was interested in the steam-engine, it must be admitted that he always showed a more profound interest in some form of engine which should be able to displace it with a superior efficiency; and hence his long series of efforts relating to the flame-engine, the caloric engine, the gas-engine, and finally the solar engine,--with either steam or heated air as the medium for carrying the heat. During the last years of his life some of his most patient and careful study was given to the perfection of a solar engine, or engine for utilizing directly the heat of the sun instead of that of coal or other carbon compounds. Besides this direct line of study and experimentation, he gave during these years much thought to various scientific problems connected with solar energy, the tides, gravitation, the nature of heat, etc., etc. A plan for deriving power direct from the tides, improvements in high-speed engines for electric-lighting purposes, further improvements in his hot-air engine in small sizes for commercial purposes,--these are some of the further lines of work which occupied the attention of his closing years.
But the most cunningly devised of all mechanisms, the heart and brain, must sooner or later tire and cease from their labors. The motive energy becomes exhausted, and the mechanism must cease its work. So it was with John Ericsson. In the first hour of the morning of March 8, 1889, Ericsson died. This was within one day of the twenty-seventh anniversary of the battle at Hampton Roads, the event with which the name of Ericsson will always be associated, and which has given to it a significance that will never be forgotten. His remains were first interred in New York, and then, in 1890, in accordance with the request of the Swedish Government, they were returned with impressive services to his native land, where they now rest. In his death he received his highest honors, for his remains were conveyed across the Atlantic by the U.S.S. "Baltimore," one of the new ships of the navy specially detailed for that service, and on both sides, in the United States and in Sweden, the event was marked with every honor and ceremony which could indicate the significance of his life and services for his adopted land and for the world at large.
The two pieces of work which perhaps will be most permanently linked with the name of Ericsson are the screw-propeller as a means of marine propulsion, and the "Monitor" as a type of warship. In addition to these, however, his life-work was rich in results which bore direct relation to many other improvements in the broad field of marine engineering and naval architecture. Of these a few of the more important may be mentioned, such as the surface condenser, distiller, and evaporator, forced draft for combustion, placing machinery of warships below the water-line, and their protection by coal, ventilation by fan-blowers, together with a vast variety of items involved in the conception and design of the "Monitor" as a whole, and in his other naval designs.
In order to appreciate the influence of Ericsson's life and work on the field of marine construction, a brief glance may profitably be taken at this branch of engineering work as it was before Ericsson's time, and as it is now.
The material employed for shipbuilding was almost entirely wood. This was displaced in the 'sixties and 'seventies by iron, which in turn was displaced by steel, so that at the present time, except for special reason, no material other than steel is thought of for this purpose. With the gradual displacement of wood by iron in the mercantile marine, Ericsson's relation was only indirect. Some of the earlier mercantile vessels in which he was interested were of wood and some of iron. In the field of warship construction, however, his influence through the "Monitor" was more direct, especially as to the value of metal armor as a protection against great gun-fire. Still, it is no more than justice to say that with the change from wood to iron which took place during the active part of his life, Ericsson had only an indirect relation, and the change would doubtless have come about at the same time, and in much the same general way as it did, independent of any influence which his work may have had upon the question. Turning to the means of propulsion, we find sails as the main, or almost only, reliance during the early years of the century. The steam-engine operating paddle-wheels had come to be recognized as a possibility, and under certain conditions as a commercial success. The screw-propeller as a means of propulsion was known only as a freak idea, and was without status or recognition as a commercial or practical means for propelling ships. So far as the screw-propeller was thought of as a means of propulsion, it lay under a suspicion of loss of efficiency due to the oblique nature of its action, and this was supposed to be such as to render it necessarily and essentially less efficient than the paddle-wheel.
Ericsson lived to see the use of sails almost entirely discarded for war purposes, and for mercantile purposes relegated to ships for special service and of continually decreasing importance. He lived to see the steam-engine take its place as the only means for supplying the power required to propel warships, and attain a position of almost equal relative importance in the mercantile marine. He lived to see the paddle-wheel grow in importance and estimation as a means of propulsion only in turn to be supplanted by the screw-propeller, which gradually increased in engineering favor from the days of its obscure infancy until it became the only means employed for the propulsion of ships navigating the high seas, while it had become a most serious rival to the paddle-wheel even for the purposes of interior and shallow-water navigation,--long a field considered as peculiarly suited to the paddle-wheel and to the engines adapted to its operation.
Regarding the change from wind to steam for the motive-power of ships, Ericsson did his full share among the engineers of his day, but it would be unfair to many others to claim for him any exclusive or preponderating influence in this movement, and in such matters it is difficult to clearly define the services of any one man. The lines of progress, however, have been in accord with his studies, and his work has certainly had a most direct and powerful influence upon the movement. The most important points of contact between Ericsson's work and these advances were in connection with his introduction of the surface condenser, the use of artificial draft, devices for heating feed water, his studies in superheated steam and its use, and his work in connection with the development of the compound principle in steam-engines, his relation to the introduction of the screw-propeller, and to the use of twin screws at a later time. He also devised and adapted many new types of engines for marine purposes, having respect to the geometrical character of the connections by means of which a reciprocating motion of the piston may be transformed into a rotary motion of the shaft. In particular, he was the first to introduce and show the advantages of engines directly connected to the propeller-shaft, instead of through the more indirect and clumsy modes which others had previously thought necessary.
Aside from his relation to the screw-propeller, perhaps no item of his work in connection with the steam-engine is of more importance than the surface condenser, with its variant forms in the distiller and evaporator. If Ericsson had done nothing else, his claims to recognition and remembrance as an engineer and benefactor might have been well founded on his work in this connection. As it is, the fact that he was so largely instrumental in their perfection and adaptation to marine uses is wellnigh forgotten in the brighter light of his other achievements.
Regarding Ericsson's relation to the successful introduction of the screw-propeller, little need be added to what has already been said. Whatever may be urged regarding dates and patents or earlier years in which the screw-propeller was used, it is a fact that in 1833-35 it was not recognized as an accepted mode of propulsion. While known as a possibility, it had no standing in the engineering practice of the day. A few years later it was recognized as an accepted mode of propulsion and had gained a permanent and definite place in the practice of the day,--a place which has continued to grow in importance until its earlier rival, the paddle-wheel, is almost on the brink of relegation to museums of antiquities, except possibly for rare and special shallow-water uses. A careful and dispassionate study of the facts, so far as they can be known at the present time, seems to indicate clearly that of those who were concerned in successfully adapting the screw-propeller to the needs of marine propulsion and in laying the foundation for these changed conditions, especially in the United States, none was so prominent as Ericsson, or so fairly deserving of the chief credit; and with this judgment the mature thought of the present day seems to agree with little dissent.
Turning to a consideration from a similar point of view of Ericsson's services in connection with warship design and construction, note may be first taken of the condition of the art of naval warfare in the years 1840-50, or when Ericsson first began his labors in this field.