The Great 19th-Century Green Spectacle Craze

Long before mirrored sunglasses were adopted as a fashion in the 20th century, spectacles with dark green glass lenses were a popular fad in the 19th. We look at several examples, cited in the writings of famous authors of the period. Dark Green lenses were not only viewed as providing relief for bright light, were held to project a certain sophistication of appearance, and they had novelty value that made them popular. But why did dark glasses become such an affectation in the 19th century, and not earlier? What did it suggest?

The Secrets of X-Ray Spex

X-Ray Spex are cheap cardboard or plastic “glasses” that are sold in novelty stores and through magazine advertisements. They produce the illusion of x-ray vision, with the viewer apparently able to see the bones in their fingers, or to see a person’s body under their clothes. How do the spectacles work, and how could the effect be done so cheaply? Who first discovered this effect and capitalized on it? Modern “x-ray spectacles” are constructed differently from the “classic” ones. How do they differ, and why did they change the design?

The Trilobite’s Eye

The eye of the trilobite has a lens not made of modified chitin or any of the usual optical materials, but of birefringent calcite. Although the trilobite was one of the most common of sea arthropods in the Cambrian period, it became completely extinct at the end of the Permian period, before the advent of the dinosurs. Very few creatures today have calcite lenses. Certainly one of the features that makes a calcite lens undesirable is that it is a birefringent crystal, and the refractive index varies considerably with direction and polarization. This make it difficult to bring light to a tight focus. Yet the trilobites persisted for twice as long as the dinosaurs did. How can an eye using a calcite lens possibly work?

The Best Disinfectant

People have known of the effectiveness of sunlight in helping people recover from illness, and early work on bacteria showed that sunlight could indeed kill micro-organisms. The efficacy of sunlight as a germicidal agent was worked into sanitation designs from the turn of the century. Then it was learned that ultraviolet light with wavelengths shorter than those transmitted by the atmosphere were even more effective at killing germs. Recently SODIS—SOlar DISinfection of contaminated water, a very simple process that uses only ordinary sunlight and no shortwave rays—provides a surprisingly effective, low-tech method for killing harmful microorganisms in water. How can this possibly work?

Thoreau’s Rainbow

In his famous book Walden, or Life in the Woods, Henry David Thoreau writes about the experience of walking through a rainbow. Since Thoreau is often praised for the accuracy of his observations of natural phenomena, what are we to make of this plainly unscientific description of a rainbow? A rainbow is a phenomenon that is always about 138 degrees (180 degrees – 42 degrees) away from the sun, and the impossibility of ever reaching it is enshrined in such stories as the Gold at the End of the Rainbow. Was he mistaken, or was he describing an emotional reaction to a natural wonder? And how critical should we be of him?

Friedrich Richard Ulbricht’s Kugelphotometer

With the rapid development of many new and varied sources of light in the 19th century—Argand lamps of different designs and which burned various fuels, Carcel lamps, stearin candles, paraffin candles, and spermaceti candles, electric arc lamps, Drummond lamps, incandescent lamps with various filaments, Nernst glowbars, and many others —some method was needed to compare their output. But with the sources varying in spectral content and the angular distribution of the light, how could a meaningful comparison be made? After various fruitless attempts were made to concentrate the light onto a uniform region a surprisingly simple solution was proposed.

Fringe Science

The Colmascope and the Polariscope are devices consisting of polarizers oriented with their polarization axes normal to each other andwith a gap between them that allows one to place objects in the gap in order to observe birefringence. It is useful for detecting stresses in glass and plastic, for identifying and orienting crystals, and for determining uniformity of transparent materials. The modern device uses two sheets of flat polarizing material. But the device predates George Eastman’s invention of Polaroid sheet. How did they use crossed polarizers before that time, and how did that differ from the current device? And what are Landolt fringes?

Who Invented the Black Light?

If you ask a search engine, “Who invented the black light?,” odds are very good that the answer you will receive is “Dr. William H. Byler in 1935.” But, in fact, Dr. Byler never claimed to have invented the long-wave ultraviolet light, no such invention is recorded in any of his papers or patents, and what is certainly what we today call the “blacklight” was invented over fifteen years earlier. So who really did invent it, and how did Byler’s name and date get on it? We look into the history and development of the ultraviolet lamp and at the work of Dr. Byler.

Lacemaker’s Lamps

In the years before the 19th century, the options for indoor lighting were limited and sometimes expensive. Yet artisans such as lacemakers, cobblers, and jewelers needed good lighting for their precise and delicate work. But not being very well paid, they needed a solution that would allow as many of them as possible to share the expense of lighting for work. How did they manage after the sun went down, especially in northern countries with long periods of winter darkness? Can the solutions they came up with be applied to present-day problems?

The Claude Lorrain Mirror

In the late 18th century, aesthetes would tour the countryside to view scenes in a device called the Claude Lorrain mirror. The Claude Lorrain mirror was a black convex mirror that was stored in a padded case. Viewers would set up the scene with great care, holding the mirror before them and looking at the scene behind them in reflection, as if arranging the shoot for a photograph. But there was no way that they could subsequently record the scene, since the samera had not yet been invented, and so they only had their memories of the image so carefully created. How did these devices work, and why did people use them?