Famous Men of Science

by Sarah Knowles Bolton

"To Henry, therefore," says Mr. Taylor, "belongs the exclusive credit of having first constructed the magnetic 'spool' or 'bobbin,' that form of coil since universally employed for every application of electro-magnetism, of induction, or of magneto-electrics. This was his first great contribution to the science and to the art of galvanic magnetization....

"But, in addition to this large gift to science, Henry has the preëminent claim to popular gratitude of having first practically worked out the differing functions of two entirely different kinds of electro-magnet; the one surrounded with numerous coils of no great length, designated by him the 'quantity' magnet, the other surrounded with a continuous coil of very great length, designated by him the 'intensity' magnet.... Never should it be forgotten that he who first exalted the 'quantity' magnet of Sturgeon from a power of twenty pounds to a power of twenty hundred pounds was the absolute CREATOR of the 'intensity' magnet; and that the principles involved in this creation constitute the indispensable basis of every form of the electro-magnetic telegraph since invented."

Professor Silliman of Yale College said: "Henry has the honor of having constructed by far the most powerful magnets that have ever been known; and his last, weighing (armature and all) but 82½ pounds, sustains over a ton;—which is eight times more powerful than any magnet hitherto known in Europe."

"In 1831," says Professor Henry, "I arranged around one of the upper rooms of the Albany Academy a wire of more than a mile in length, through which I was enabled to make signals by sounding a bell. The mechanical arrangement for effecting this object was simply a steel bar, permanently magnetized, of about ten inches in length, supported on a pivot, and placed with its north end between the two arms of a horse-shoe magnet. When the latter was excited by the current, the end of the bar thus placed was attracted by one arm of the horse-shoe and repelled by the other, and was thus caused to move in a horizontal plane and its further end to strike a bell suitably adjusted." This was the first "sounding" electro-magnetic telegraph. With this growing fame he was not disposed to think too highly of himself. A friend, noticing a look of sadness in the face of the young professor, said to him,—"Albany will one day be proud of her son;" and so it proved.

A year before this, in May, 1830, Professor Henry had married, at thirty-one, Harriet L. Alexander of Schenectady, N. Y., a cultivated and helpful woman.

In 1832, Princeton College needed a professor of natural philosophy. Henry's friends heartily commended him for the position. Silliman said,—"Henry has no superior among the scientific men of the country," and Professor Renwick of Columbia College, New York, said, "He has no equal."

After six years at the Albany Academy, Henry removed to Princeton, where for fourteen years he added constantly to his fame and usefulness by original work. Of his discoveries in these fruitful years he gives the following summary, at the request of a friend:—

"I arrived in Princeton in November, 1832, and, as soon as I became fully settled in the chair which I occupied, I recommenced my investigations, constructed a still more powerful electro-magnet than I had made before,—one which would sustain over three thousand pounds,—and with it illustrated to my class the manner in which a large amount of power might, by means of a relay magnet, be called into operation at the distance of many miles.... The electro-magnetic telegraph was first invented by me, in Albany, in 1830.... At the time of making my original experiments on electro-magnetism in Albany, I was urged by a friend to take out a patent, both for its application to machinery and to the telegraph; but this I declined, on the ground that I did not then consider it compatible with the dignity of science to confine the benefits which might be derived from it to the exclusive use of any individual. In this perhaps I was too fastidious."

Professor Asa Gray well said, "For the telegraph and for electro-magnetic machines, what was now wanted was not discovery, but invention; not the ascertainment of principles, but the devising of methods." Morse is not to be less honored because somebody discovered the principle, which he and others utilized for the race, any more than Edison, Bell, and others, because Faraday and Henry helped to make their grand work possible.

"My next investigation, after being settled at Princeton," says Professor Henry, "was in relation to electro-dynamic induction. Mr. Faraday had discovered that when a current of galvanic electricity was passed through a wire from a battery, a current in an opposite direction was induced in a wire arranged parallel to this conductor. I discovered that an induction of a similar kind took place in the primary conducting wire itself, so that a current which, in its passage through a short wire conductor, would neither produce sparks nor shocks would, if the wire were sufficiently long, produce both those phenomena....