The death of Edison’s close assistant led him to fear X-rays and cease research on fluorescent lamps.
In December 1895, German physicist Wilhelm Roentgen sent a preliminary report to the journal of the Würzburg Medical-Physical Society describing the discovery of “a new type of ray.” He named this previously undiscovered radiation X-rays. According to him, these rays could penetrate wooden blocks and thick volumes of books, even a human hand, capturing the shadow of the internal bones, as reported by Amusing Planet.
Edison looking through a fluorescent lens to observe Dally’s hand under X-rays. (Photo: Edward P. Thompson/Wellcome Images)
Within weeks, the news spread worldwide, sparking hundreds of discussions in newspapers and magazines about this new discovery and its potential applications in medicine and physics. However, radiation claimed the lives of hundreds of scientists across the globe in the decades that followed. The destructive effects of Roentgen’s rays on living tissue were predicted as early as March 1896 by Italian physicist Angelo Battelli. Some other engineers also expressed concerns, but the possibilities opened up by the discovery of X-rays led many scientists to set aside their worries in pursuit of new applications for this groundbreaking discovery. Clarence Madison Dally was among the first to embrace this new frontier.
Dally was born in Woodbridge, New Jersey, in 1865, shortly after the American Civil War ended. His father was a glassblower at the Edison Lamp Works factory in nearby Harrison, which specialized in manufacturing bulbs for Edison. At the age of 17, Dally joined the Navy, serving for six years before being discharged. He returned home to Woodbridge in 1888, where he worked alongside his father and three brothers at Edison Lamp Works.
When Roentgen announced the discovery of X-rays in 1895, Edison quickly recognized its significance and saw it as a potential tool to improve incandescent lighting. Edison was particularly interested in one of Roentgen’s experiments, in which he coated a screen with barium platinocyanide crystals and exposed it to X-rays. The crystals would glow in the dark when X-rays struck them. Edison believed that if he could find the right fluorescent material, he could create a screen that glowed long enough to illuminate an entire room.
Edison called Dally to assist him in this new research at the laboratory in East Orange, New Jersey. By then, Dally had become a skilled glassblower and was well-liked by Edison. He produced thousands of Crookes tubes and experimented with over 1,000 different compounds. Dally personally tested them by placing his left hand between the X-ray source and the fluorescent screen, exposing himself to unsafe doses of X-rays. Eventually, Dally discovered that calcium tungsten glowed nearly 12,000 times brighter than the barium platinocyanide used by Roentgen. Edison had found a new fluorescent lamp but would pay a heavy price for it.
Edison found it difficult to focus with his left eye. An ophthalmologist suggested that this was due to prolonged use of the fluorescent lens. This device used X-rays to stimulate fluorescent compounds and had an opening to look through. Edison warned Dally about the risks of continuing to use the Crookes tubes, but Dally dismissed the warning and insisted on using the strongest tubes he could find.
Before long, Dally noticed his hair gradually falling out, followed by his eyebrows and eyelashes. His face became wrinkled, and his left hand swelled painfully. “Then, arteriosclerosis appeared, spreading to the smallest blood vessels in his hand,” noted W.B. Graves, Dally’s doctor. “He was not paralyzed, but the blood vessels gradually shrank, depriving tissue of nutrients and preventing the swelling in his left hand from healing. The right hand was also affected, including the fingertips, although the condition was not as severe as the left hand.”
Dally did not believe that his illness could threaten his life. When his left hand began to have problems, he used his right hand. At night, he slept with both hands submerged in water to relieve the burning sensation. Like many researchers of that era, Dally thought he would recover once he stopped working with the tubes.
By 1900, the damage to Dally’s hand developed into cancer, spreading from his hand to his forearm. After many attempts to treat it, doctors had to amputate his left arm. Dally also lost four fingers on his right hand, leaving only his thumb. Despite these surgeries, doctors could not prevent the cancer from metastasizing. Dally passed away four years later, in 1904, due to mediastinal cancer.
Dally’s death made Edison fearful of X-rays. Subsequently, he ceased research on fluorescent lamps. “I do not want to learn anything more about X-rays. In the hands of experienced individuals, it is a useful tool for surgery, helping to identify objects hidden from view, such as in appendectomy. But they are also deadly in the hands of the inexperienced, including those who use them continuously for experiments,” Edison said.
