The attempt to send signals by electricity had been made many times before Henry became interested in the problem.On the invention of Sturgeon's magnet there had been hopes in England of a successful solution, but in the experiments that followed the current became so weak after a few hundred feet that the idea was pronounced impracticable.Henry strung a mile of fine wire in the Academy, placed an "intensity" battery at one end, and made the armature strike a bell at the other.Thus he discovered the essential principle of the electric telegraph.This discovery was made in 1831, the year before the idea of a working electric telegraph flashed on the mind of Morse.There was no occasion for the controversy which took place later as to who invented the telegraph.That was Morse's achievement, but the discovery of the great fact, which startled Morse into activity, was Henry's achievement.In Henry's own words: "This was the first discovery of the fact that a galvanic current could be transmitted to a great distance with so little a diminution of force as to produce mechanical effects, and of the means by which the transmission could be accomplished.I saw that the electric telegraph was now practicable." He says further, however: "I had not in mind any particular form of telegraph, but referred only to the general fact that it was now demonstrated that a galvanic current could be transmitted to great distances, with sufficient power to produce mechanical effects adequate to the desired object."** Deposition of Joseph Henry, September 7, 1849, printed in Morse, "The Electra-Magnetic Telegraph", p.91.
Henry next turned to the possibility of a magnetic engine for the production of power and succeeded in making a reciprocating-bar motor, on which he installed the first automatic pole changer, or commutator, ever used with an electric battery.He did not succeed in producing direct rotary motion.His bar oscillated like the walking beam of a steamboat.
Henry was appointed in 1839.Professor of Natural Philosophy in the College of New Jersey, better known today as Princeton University.There he repeated his old experiments on a larger scale, confirmed Steinheil's experiment of using the earth as return conductor, showed how a feeble current would be strengthened, and how a small magnet could be used as a circuit maker and breaker.Here were the principles of the telegraph relay and the dynamo.
Why, then, if the work of Henry was so important, is his name almost forgotten, except by men of science, and not given to any one of the practical applications of electricity? The answer is plain.Henry was an investigator, not an inventor.He states his position very clearly: "I never myself attempted to reduce the principles to practice, or to apply any of my discoveries to processes in the arts.My whole attention exclusive of my duties to the College, was devoted to original scientific investigations, and I left to others what I considered in a scientific view of subordinate importance--the application of my discoveries to useful purposes in the arts.Besides this Ipartook of the feeling common to men of science, which disinclines them to secure to themselves the advantages of their discoveries by a patent."Then, too, his talents were soon turned to a wider field.The bequest of James Smithson, that farsighted Englishman, who left his fortune to the United States to found "the Smithsonian Institution, for the increase and diffusion of knowledge among men," was responsible for the diffusion of Henry's activities.
The Smithsonian Institution was founded at Washington in 1846, and Henry was fittingly chosen its Secretary, that is, its chief executive officer.And from that time until his death in 1878, over thirty years, he devoted himself to science in general.
He studied terrestrial magnetism and building materials.He reduced meteorology to a science, collecting reports by telegraph, made the first weather map, and issued forecasts of the weather based upon definite knowledge rather than upon signs.
He became a member of the Lighthouse Board in 1852 and was the head after 1871.The excellence of marine illuminants and fog signals today is largely due to his efforts.Though he was later drawn into a controversy with Morse over the credit for the invention of the telegraph, he used his influence to procure the renewal of Morse's patent.He listened with attention to Alexander Graham Bell, who had the idea that electric wires might be made to carry the human voice, and encouraged him to proceed with his experiments."He said," Bell writes, "that he thought it was the germ of a great invention and advised me to work at it without publishing.I said that I recognized the fact that there were mechanical difficulties in the way that rendered the plan impracticable at the present time.I added that I felt that I had not the electrical knowledge necessary to overcome the difficulties.His laconic answer was, 'GET IT!' I cannot tell you how much these two words have encouraged me."Henry had blazed the way for others to work out the principles of the electric motor, and a few experimenters attempted to follow his lead.Thomas Davenport, a blacksmith of Brandon, Vermont, built an electric car in 1835, which he was able to drive on the road, and so made himself the pioneer of the automobile in America.Twelve years later Moses G.Farmer exhibited at various places in New England an electric-driven locomotive, and in 1851Charles Grafton Page drove an electric car, on the tracks of the Baltimore and Ohio Railroad, from Washington to Bladensburg, at the rate of nineteen miles an hour.But the cost of batteries was too great and the use of the electric motor in transportation not yet practicable.
