a website collaboration between Science Service and the Smithsonian Institution

1928 - the replica designed by lamp engineers of the General Electric Company from authoritative recollections of Edison's men and of Edison himself


CD 1963100 E&MP 25.040

Electric Lamps

October 27, 1928

Edison's original electric light looked like this [right]. The actual lamp was destroyed in order to examine the filament. The 49th anniversary of its sucess was marked by the presentation to Edison of the Congressional medal.

Feature Story:

Among her sons of achievement America boasts only one “wizard” of invention. She has had a host of inventors but still only one “wizard.”

To capture the human voice upon a cylinder of wax; to produce pictures in which the people move as they do in actual life; to imprison a hair-like thread within vacuum and make it glow electrically with such brilliance as to furnish the people with a wonderfully useful lamp–these things are magical indeed. And these things all shout the same magical name. It is the name of Edison.

As the “wizard of Menlo Park” began the golden jubilee year of his incandescent electric light. America paid him homage of a singular sort. Acting as representative all his fellow-Americans, the Secretary of the Treasury, Andrew W. Mellon, presented him last Saturday night October 20, with a special Congressional gold medal, of which the obverse forms our cover design this week. The ceremony was broadcast by radio; and the President of the United States spoke to the nation from Washington, to remind the millions who listened to the influence Edison has been in their daily living.

At the same time Edison renewed his acquaintance with an old friend for there was returned to him the original phonograph, with which, in 1877 he reproduced his own recitation of “Mary had a little lamb” For many years this has reposed in the Science Museum at South Kensington, London, but Donald Campbell of the British Embassy gave it back to him.

The ceremony however was in commemoration of the electric lamp, because the incandescent lamp is generally appreciated as Edison’s highest contribution to the national wealth. He himself once described it as “the most satisfactory of my inventions to contemplate.”

The incandescent lamp however was born amid storm and stress, amid the thunderings of skeptics.In the world at large, especially the scientific world, there was heard the turbulent clash of carping voices whenever Edison and his electric illumination scheme were touched upon.

Yet, in the system solitude of Menlo Park, New Jersey, fifty years ago, there was merely intensive industry.The days slipped by untroubled then unheeding–busy, indeed, but calm.

The bright autumn sun poured in through those tall, unshaded laboratory windows. Men came and went, absorbed in curious tasks. At one of the worktables sat Charles Batchellor, the model-maker, whose delicate fingers patiently struggled to mount a slender bit of carbonized cotton thread upon a little stem of glass. Beside him, watching, assisting, directing, sat Edison.

As the October day drew to a close, the setting sun drew to a close, the setting sun threw crimson rays across the long bare floors, and the rows of bottles lining the shelves, the tables with their crowded paraphernalia, the tall Sprengle mercury pump, the fat, sprawling coal stove gleamed in the weird red light. The silent figures bending over the table became silhouettes of fiery outline, and their shadows loomed gigantic upon the opposite wall. The scene suggested the lair of some alchemist of old, a place of wonder-doings, a den of magic-as it were.

That evening the work went on. It continued until past midnight, as it often did. The next morning the new experimental lamp–the thin filament encased in its bulb of glass–was taken over to the Sprengle pump and carefully attached o the exhaust mechanism, to have the air pumped out.

Edison watched all that day as the pump worked on. At last he connected the lamp to his large bichromate battery and every now and then he sent an electric current through the bulb. Instantly the gases burned in the filament began pouring out. The pump worked on for hours longer; and Edison stayed at his post, “doctoring “ the lamp with frequent doses of electricity, until the highest possible vacuum existed inside that little bulb–one millionth of an atmosphere.

It was eight o’clock in the evening of October 21, 1879. Edison, satisfied with his work thus far, spoke tersely to young Francis Jehl, the pump-tender. He sent for Ludwig Boehm, the glass blower, who carefully sealed of the lamp and helped Jehl mount in on the test-stand to undergo its life-test.

A few minutes late the spot of yellow incandescence began to glow: and then the little group took up what Jehl always afterward called the “death watch.”

“We had tested many lamps before that day,” Jehl recalls. “And none had come up to the mark that Edison sought. With this new lamp we did not know the result would prove any better. The life-test alone as all previous cases, would decide the question of success or failure. The one thing we wanted to know was how long the lamp would last–how long a life it was good fore–how soon it would show signs of burning out. So we began the death–watch the death–watch of an incandescent lamp which, unknown to any of us, was the future.”

That watch lasted forty hours. For forty hours the lamp glowed steadily–all the rest of the night, and until about one o’clock in the afternoon of the second day. Never once in that interval was it without observers.

Edison himself sat there as unmoved as a Stoic–a lean, well-knit, youthful figure, without coat, collar or tie, and wearing a black skull cap which he frequently exhibited in those days. Once only he relaxed, searching full-length upon a nearby laboratory table for two or three hours’ sleep, while his faithful henchmen kept the vigil–Jehl, Batchellor, Francis R. Upton, his mathematician, occasionally Ludwig Boehm and Martin Force, and even sturdy John Krensi, his machinist, the first man besides Edison ever to hear the human voice by phonograph.

When the “wizard awoke, the lamp still glowed. He and Upton measured its electrical resistance–one the basic characteristics that made possible Edison’s triumph where others had failed.

Then the watch went on–Edison in silent contemplation, dreaming a bit, as he realized the goal was at hand, of “great central stations in many cities, supplying electric current for large numbers of incandescent lamps.” That was his broad economic conception his “complete system of lighting,” which he even then had clearly planned in every detail.

At last the glowing filament burned out. But they knew success was theirs. Edison exclaimed to his assistants, in quiet, equanimous elation: “That’s fine, boys, fine! If the lamp will burn forty hours now, I know I can make it last hundred.” Before many months had passed he had made it last a thousand.

The first thing he did, however, was to deliberately break that glass bulb and carefully remove the filament for a microscopic examination. It was his invariable practice; nothing that could possibly add to his knowledge of incandescent lighting was ever left undone.

That is why the original forty-hour lamp no longer exists. It cannot be enshrined in any museum, not even Henry Ford’s growing aggregation of Edisonian treasures. The nearest approach to it is the replica [image above] designed by lamp engineers of the General Electric Company from authoritative recollections of Edison’s men and of Edison himself. 

Feature Story by Science Service, Vol. XIV

National Museum of American History


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