Brilliant_ The Evolution of Artificial Light - Jane Brox [86]
Even a few fireflies might provide enough light by which to see. At the end of the nineteenth century, in the Smithsonian Institution light collection, there was a dark lantern said to have been used by a thief in Java. The shallow wooden bowl had been fashioned with a pivoting lid that could be used to hide the light in a hurry. The thief lined the cup of the lantern with pitch and stuck several fireflies to it. When one firefly perished, he replaced it with another from a store he kept in a capped cane stalk.
In the southern regions of the Western Hemisphere, people sometimes saw by the glow of a bioluminescent click beetle, Pyrophorous noctilucus, which emits a constant green light. A history of Hispaniola written in 1725 attests:
There were at first found a sort of vermin, like great beetles, somewhat smaller than sparrows, having two stars close by their eyes and two more under their wings, which gave so great a light that by it they could spin, weave, write, and paint; and the Spaniards went by night to hunt the Utias, or little rabbits of that country ... carrying those animals tied to their great toes or thumbs.... They took [the beetles] in the night with firebrands because they made to the light and came when called by their name, and they are so unwieldly [sic] that when they fall they can not rise again; and the men stroaking [sic] their faces and hands with a sort of moisture that is in those stars, seemed to be afire as long as it lasted.
These beetles are the brightest of all luminous insects—the Spanish conquistador Bernal Díaz del Castillo, thought a flurry of them were the matchlocks of his enemies—and during nights of almost complete darkness, the beetles in any number must have seemed magical and spectacular, though they are actually less than two inches long (nowhere near the size of sparrows), and few of us today would think them bright enough to help us work or walk.
Steinmetz had put great store in Harvey's work on bioluminescence: "I think it is possible that twenty years from now it may be a thing of tremendous practical importance.... There is, of course, no absolutely cold light, but there are experiments on many which may be called comparatively cold.... There are none, however, which compare with that of Dr. Harvey, in its promise of working at low cost. All other kinds require coal or energy of some other kind to produce electrical power." Throughout his decades of research, Harvey succeeded in understanding more clearly the way bioluminescence works, and he was even able to diffuse enough luciferin in a flask of water to create a light steady enough to read a newspaper by. But neither he nor anyone else managed to turn it into a practical light for industrial society.
The nearest researchers came to cold light in the 1930s was the fluorescent tube, which uses about a quarter of the energy and emits a quarter of the heat of incandescent bulbs of the same strength. It's a descendant of nineteenth-century discharge lamps, which used various gases and combinations of gases to create different-colored lights: neon for red, argon for lavender, mercury and argon together for blue, and helium for yellow. All such lights eventually came to be popularly known as "neon lights," and although they proved to be ideal for signs and advertising, researchers were unable to find a gas alone or in combination that could produce a practical white light for workplaces or homes. Peter Cooper Hewitt came closest, just after the turn of the twentieth century. He fabricated a mercury vapor lamp—a four-foot-long tube that shone greenish blue—which could