There is no record of Henry having returned again, and he disappeared into the murk of history. The cave location faded away, and the story became one of the colorful, spooky legends to be told around campfires after dark up in the Ozarks. That’s the story, but it was not written down until 34 years after the incident, and facts could have drifted. There are questions. The initial problem was obviously oxygen deprivation, but what had taken the place of normal air in this cave? It could have been methane, the scourge of coal mining, but the cave was not lined with coal and there was not a hint of tool marks anywhere. And what had caused the burn-like lesions all over Bill Henry? Was he alone allergic to some mineral on the walls? What was the bright, iridescent stuff lining the cave? That is not what silver, or even gold, looks like in its native state. Later explorations of the cave would provide unexpected answers to these questions.
Meanwhile, in the formal physics lecture theaters and laboratories in Europe in 1879, the danger of being in a certain cave in Missouri and what it had to do with anything were unknown. Scientists across the Continent and in the United Kingdom, working at well-established universities, were busy studying the interesting properties of electricity in evacuated glass tubing. A thrillingly dangerous piece of equipment called a Ruhmkorff coil produced high-voltage electricity for these experiments. They were essentially inventing and refining what would become the neon sign. Research was progressing at an appropriate pace, gradually unraveling the mysteries of atomic structure.
Working independent of any academic pretension in the United States was a highly intelligent, well-educated immigrant from Croatia, Nikola Tesla. He came ashore in June 1884 with a letter of introduction to Thomas Edison, famous American inventor of the record player and the light bulb. He was given an engineering job at $18 a week improving Edison’s awkward and ultimately unusable DC electrical power system, but he quit a year later under intractable disagreements concerning engineering practice, salary, general company philosophy, and his boss’s personal hygiene. He immediately started his own power company, lost control of it, and wound up as a day laborer for the Edison Company laying electrical conduit. Not seeing a need for sleep, he spent nights working on high-voltage apparatus and an alternating-current induction motor.
In Europe they were working with induction coils that could produce a ripping 30,000 volts, stinging the eyes with ozone wafting out of the spark gap and with a little buzzer on the end making the spark semi-continuous. In New York, Tesla was lighting up the lab with 4,000,000 volts and artificial lightning bolts vibrating at radio frequencies. Naturally drawn to the same rut of innovation as his Old World colleagues, he connected an evacuated glass tube to his high-voltage source in April 1887. It had only one electrode. He connected it to his lightning machine and turned it on, just to see what would happen. Electrons on the highly over-driven electrode slammed themselves against the glass face of the tube, trying desperately to get out and find ground somewhere. The glass could not help but fluoresce under the stress, making a weak but interesting light. Tesla had invented something important, but he would not know exactly what it was until years later. He applied for a patent for his single-electrode tube, calling it an “incandescent light bulb” as a finger-poke in Edison’s eye.
In 1891 Tesla’s fortunes improved considerably when George Westinghouse, Edison’s competitor for the electrical power market, became interested in his alternating current concepts. He moved into a new laboratory on Fifth Avenue South, and he had room to spread out and really put his high-voltage equipment to use. One night, he connected up his single-electrode tube built back in 1887. He turned off all the lights so he could see arcs and electron leakage. To his surprise, something invisible was coming out the end of his tube and causing the fresh white paint on the laboratory wall to glow. Curious, he put his hand in the way. His hand did stop the emanations, but only partly. The bones in his hand were dense enough to stop it from hitting the wall, but not the softer parts, and he could see his skeletal structure projected on the paint. Tesla, fooling around in his lab after hours, had invented radiology. In the next days he substituted photographic plates for the wall, and made skeletal photos of a bird, a rabbit, his knee, and a shoe with his foot in it, clearly showing the nails in the sole.
Unfortunately, Tesla was pulled toward greater projects, and he failed to pursue the obvious application of this discovery.
Four years later, on December 28, 1895, the discovery of the unusual radiation was formally announced, not by Tesla, but by Wilhelm Röntgen, working at the University of Munich. Röntgen was also studying fluorescence, using his trusty Rhumkorff apparatus and a two-electrode tube custom-built by his friend and colleague, Phillipp von Lénárd.[6] Like Tesla, he was startled to notice that some sort of invisible emanations from the tube pass through flesh, but are stopped by bones or dense material objects. In his paper in the Proceedings of the Physical Medical Society, Röntgen gave the phenomenon a temporary name: x-rays. Amused at reading the paper, Tesla sent Röntgen copies of his old photo plates. “Interesting,” replied Röntgen. “How did you make these?” Not trusting his own setup to be kind, Röntgen covered his apparatus with sheets of lead, with a clear hole in the front to direct the energy only forward.
Tesla, on the other hand, put his head in the beam from his invention and turned it up to full power, just to see what it would do. Röntgen had jumped him on the obvious medical usage, but there had to be some other application that could be exploited for profit. After a short while directly under the tube, he felt a strange sensation of warmth in the top of his head, shooting pains, and a shock-effect in his eyes. Seeing the value of publication shown by Röntgen’s disclosure, he wrote three articles for the Electrical Review in 1896 describing what it felt like to stick your head in an x-ray beam.
The effects were odd. “For instance,” he first wrote, “I find there is a tendency to sleep and I find that time seems to pass quickly.” He speculated that he had discovered an electrical sleep aid, much safer than narcotics. In his next article for 1896, after having spent a lot of time being x-rayed, he observed “painful irritation of the skin, inflammation, and the appearance of blisters …, and in some spots there were open wounds.” In his final article of 1896, published on December 1, he advised staying away from x-rays, “… so it may not happen to somebody else. There are real dangers of Röntgen radiation.”
These writings were the first mention in technical literature of the hazards of over-exposure to the mysterious, invisible rays. For the first time in history, something that human senses were not evolved to perceive was shown to cause tissue damage. The implication was a bit terrifying. It was something that could be pointed at you, and you would not know to get out of the way. Some of the effects were even delayed, and at a low rate of exposure, which was completely undetectable, one could be endangered and not even know it. The effect was cumulative. Tesla’s equipment was powerful. He was fortunate not to have set his hair on fire, but his health was never quite the same.
At the Sorbonne in Paris in 1898, Marie Curie, with some help from her husband, Pierre, discovered a new element, named “radium,” in trace quantities mixed into uranium ore. It had invisible, energetic influences on photographic plates, just as her thesis advisor, Henri Becquerel, had found in uranium salt two years before. She named the effect “radiation.” It was similar in character to Röntgen’s x-rays, only these came streaming freely out of a certain mineral, without any necessary electricity. A clue to the relation was its curious property of encouraging the formation of sores on flesh that was exposed to it.
6
Röntgen could have mail-ordered a mass-produced vacuum tube, called a Pulyui Lamp, from Poland and saved himself some time, if communications and advertising technology had been what they are today. Ivan Pulyui, a college professor at the University of Vienna from the Ukraine, is sometimes credited with having sold the first x-ray tubes, before the x-ray was discovered. The claim is semi-true. His Pulyui Lamp was available perhaps as early as 1882, but it was sold as a light bulb, and Pulyui did not realize that it was streaming x-rays along with a blue glow until he read Röntgen’s paper in 1895. Pulyui immediately saw the medical diagnostic use of x-rays, and his lamps became quite useful.