Show & Tell: The Lamp That Saved Coal Miners' Lives

Paul Wilkinson

Coal, as the chemist Sir Humphry Davy observed in his 1818 book describing the development of this Davy Safety Lamp, was at the heart of much of early 19th-century England’s industrial progress. “Essential in affording warmth and preparing food, it yields a sort of artificial sunshine, and in some measure compensates for the disadvantages of our climate,” he wrote. “By means of it, metallurgical processes are carried on, and the most important materials of civilized life furnished … Not only manufactories and private houses, but even whole streets are lighted by its application.”

Yet this wonderful material needed to be mined by men (and boys) who were taking great risks with their lives. Ironically enough, given coal’s light-giving properties, one of their major problems as workers was illumination. Miners carrying lamps could run into pockets of methane gas, then often called firedamp, which would explode when it came into contact with the flame. (An 1883 glossary of mining terms tells us that miners called cavities in coal seams “bags of foulness,” an epithet that gives some sense of their dread of such spots.)

In his book On the Safety Lamp for Coal Miners, Davy describes—in a deliberately dry fashion intended to forestall morbid curiosity—the effects of such explosions:

The phenomena are always of the same kind. The miners are either immediately destroyed by the explosion, and thrown with the horses and machinery through the shaft into the air, the mine becoming as it were an enormous piece of artillery, from which they are projected; or they are gradually suffocated, and undergo a more painful death from the carbonic acid and azote remaining in the mine after the inflammation of the fire damp; or what, though it appears the mildest, is perhaps the most severe fate, they are burnt or maimed, and often rendered incapable of labor and of healthy enjoyment for life.

In 1812 a firedamp explosion in the Felling mine, in northeast England near Newcastle, killed 92 workers. In the aftermath, a concerned clergyman asked Davy, who was employed by the Royal Institution as a chemist, experimenter, and public educator, and who had by that point in his career gained both fame and a knighthood, to find a safer way to illuminate the mines.

Davy experimented on the lamp in his London laboratory throughout the fall of 1815. Given the contemporary level of understanding of the action of flame, his experiments were quite dangerous. He eventually arrived at a design that seems, in retrospect, obvious: a flame surrounded by iron wire gauze, which would allow light out, but absorb the heat that caused the explosions.

Image credit: Paul Wilkinson

Davy’s lamp was widely adopted after successful tests in January 1816. Although he was urged to patent the invention, he decided not to profit off of the design. Even though he didn’t claim intellectual priority, he found himself drawn into a fight with engineer George Stephenson, who had invented a different, less effective kind of safety lamp at the same time, and needed to prove that he had come up with the idea first. Davy eventually won that battle, but Stephenson was to go on to make a different kind of mark on the industrial landscape by inventing and perfecting the first steam-powered locomotive.  

Biographer Richard Holmes writes that despite his refusal to patent the lamp, Davy was nonetheless “hugely proud of his achievement, and was never modest about it.” The chemist received a medal from the Royal Society and was made a baronet; he even “designed his own coat of arms, showing the safety lamp encircled with a Latin motto which announced: ‘I Built The Light Which Brings Safety.’”

Afternoon Map
Monthly Internet Costs in Every Country

Thanks to the internet, people around the world can conduct global research, trade tips, and find faraway friends without ever leaving their couch. Not everyone pays the same price for these digital privileges, though, according to new data visualizations spotted by Thrillist.

To compare internet user prices in each country, cost information site created a series of maps. The data comes courtesy of English market research consultancy BDRC and, which teamed up to analyze 3351 broadband packages in 196 nations between August 18, 2017 and October 12, 2017.

In the U.S., for example, the average cost for internet service is $66 per month. That’s substantially more than what browsers pay in neighboring Mexico ($27) and Canada ($55). Still, we don’t have it bad compared to either Namibia or Burkina Faso, where users shell out a staggering $464 and $924, respectively, for monthly broadband access. In fact, internet in the U.S. is far cheaper than what residents in 113 countries pay, including those in Saudi Arabia ($84), Indonesia ($72), and Greenland ($84).

On average, internet costs in Asia and Russia tend to be among the lowest, while access is prohibitively expensive in sub-Saharan Africa and in certain parts of Oceania. As for the world’s cheapest internet, you’ll find it in Ukraine and Iran.

Check out the maps below for more broadband insights, or view’s full findings here.

Map of Internet costs in each country created by information site

Map of Internet costs in each country created by information site

Map of Internet costs in each country created by information site

Map of Internet costs in each country created by information site

Map of Internet costs in each country created by information site

[h/t Thrillist]

Can You Figure Out Why the Turtles Bulge in This Optical Illusion?

Ready for a little vision test? Akiyoshi Kitaoka, a Kyoto-based psychologist who studies visual illusions, created this eye-bending image that appears to bulge and bend. In the image, shared on, the horizontal and vertical lines actually run straight across and down, but they look like they ripple, and the shapes (Kitaoka calls them turtles) look like they’re different shades of gray, even though they’re an identical color.

As Phil Plait explains for Syfy, the key is in the corners—the turtle “legs,” if you will. “At each vertex between turtles, they form a rotated square divided into four smaller squares," he writes. "Note how they're offset from one another, giving a twist to the vertices.” If you zoom in closely on the image, the lines begin to straighten out.

The difference in the colors, meanwhile, is a result of the contrast between the black and white pixels outlining the turtles. If the outlines of the turtles were entirely black or entirely white, instead of a combination, the grays would look identical. But the contrast between the two fools your eyes into thinking they're different.

To see more of Kitaoka’s illusion art, you can follow him on Twitter @AkiyoshiKitaoka. Then, go check out these other amazing optical illusions.

[h/t Syfy]


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