January 1880: Edison's electric light

Edison, along with many others, had for some years been trying to develop a practical electric light, and our predecessors were reacting to a report in the New York Herald that he had finally succeeded. It's fair to say that they were not persuaded.

The article is headed "Mr Edison’s latest electric light" and you can almost hear the weariness in the word "latest". It starts by recalling a Charles Dickens character, who when asked their opinion of another replies that "I don't believe there is such a person". The Engineer notes that when it comes to the description of Edison by the New York Herald, it does not believe that such a person exists, and adds that it is surprised that Edison allows the claims attributed to him to be published. "We refuse to believe the latter gentleman [Edison] can hold himself responsible for the sayings and doings of his prototype", it says.

CLICK HERE TO READ THE ENGINEER'S 1880 COVERAGE OF EDISON'S LIGHT BULB

The difficulty that Edison and all the other electric light pioneers had been experiencing was to find a suitable material to form the filament of an electric lamp that would glow reliably when heated by electric current but would not disintegrate. The electric lamp described in the Herald article, it seems, used a filament of carbon inside an evacuated glass bulb, something which had already been tried unsuccessfully.

In fact, the engineer quotes JW (Joseph) Swan, in later years co-credited with Edison as the inventor of incandescent electric light, who stated in nature in January 1880 that he had tried a horseshoe-shaped carbon filament 15 years previously, and had failed. The Herald claimed that Edison had told it he had made a filament from compressed lampblack mixed with tar, which he had been rolling between his fingers while contemplating the problem (lampblack was a sticky soot produced by the incomplete combustion of oil in oil lamps). He tried this in his prototype lamp apparatus, and the result, though not completely successful, was better than he expected. This led him to try other textures of carbon that he had not previously tested, and he found that a filament made from the charred carbon remnant of a short length of cotton thread proved to be successful.

The Engineer was sceptical. "It is neither more nor less than an incandescent lamp," it says. "Such lamps have been invented and made already by the hundred, and they have failed." The length would not be able to burn continuously for at least four or five hours a night for half a year, it predicted. "It is a pretty toy and nothing more."

Some of the claims made for the lamp were "glaringly absurd," it adds. Particular scorn is poured on the claim the land could be made for 25 cents, or one shilling as it was at the time in Britain. "Is it credible," it asks, "that glass globes can be exhausted of air to the millionth of an atmosphere for one shilling?" Moreover, it notes, the filament was held in place with clamps made of platinum, and no other metal would do. "How much platinum wire do the readers of the New York Herald imagine can be got for one shilling? And what kind of skilled labour will be required to make such a thing? The notion that such a refined mathematical instrument could be made for one shilling is simply preposterous."

With hindsight we can see that the journal was quite right to be sceptical. The version of the electric lamp described by the Herald was not the final article; Edison eventually settled on carbon derived from bamboo, which again he claimed to have stumbled upon, this time while examining fibres from a bamboo fishing-rod. He patented this bulb, and claiming to be its sole inventor (though Joseph Swan had in fact got there first), marketed it throughout the US, while Swan retained the UK rights and it was 1200 of his bulbs that this lit world's first public building equipped with electric light, London's Savoy Theatre.

Swan, meanwhile, had also tried many different substances, including carbonised hairs from his luxuriant beard. Later, he made an important innovation in discovering a process for squeezing nitro-cellulose through holes to form a conducting cellulose filament. When Edison and Swan formed a joint-venture in 1883 to manufacture and market lightbulbs, it was this cellulose filament that was used. In later years, the “Ediswan” factory at Ponders End, North London, became an important centre for the manufacture of thermionic valves and cathode-ray tubes, and was important to the early years of the electronics industry.