Sir William Crookes (pronounced "crooks"; June 17, 1832 – April 4, 1919) was an English scientist who studied chemistry and physics. He attended the Royal College of Chemistry, which is now part of Imperial College London, and worked on studying light patterns. He helped develop vacuum tubes, creating the Crookes tube in 1875. By observing cathode rays in these tubes, he suggested that "radiant matter" might be a new type of matter, an important idea for understanding plasma physics.
He discovered the element thallium in 1861 using light analysis. He also described the light pattern of helium found on Earth in 1865. Crookes invented the Crookes radiometer but did not fully explain how it worked. He also created a special lens that blocked all ultraviolet light. At one time, he was interested in spiritualism and became president of the Society for Psychical Research.
Later in life, Crookes was known as a highly respected experimentalist for his creative work in physics and chemistry. He was admired for his hard work and intelligence. His studies covered both basic and practical science, as well as topics like psychic research. This made him a well-known figure and earned him many honors from the public and academic communities.
Biography
William Crookes was born in London in 1832. He was the eldest of eight children who survived childhood; eight other siblings died young. His father, Joseph Crookes, was a wealthy tailor and real estate investor from the north of England. His mother was Mary Scott. Joseph Crookes’s father, William, was also a tailor. William’s grandfather, John Crookes, was the mayor of Hartlepool, County Durham, three times.
Joseph Crookes had five children with his first wife. Two of those children, Joseph and Alfred, inherited the tailoring business. This allowed William to pursue a different path. In 1848, at age 16, Crookes began studying organic chemistry at the Royal College of Chemistry (now part of Imperial College). He lived about three miles from the college in Oxford Street. His father’s shop was about half a mile away. Crookes paid £25 for his first year of tuition and had to buy his own equipment and some chemicals. After his first year, he won the Ashburton scholarship, which covered his second year’s tuition. By the end of his second year, he became a junior assistant to August Wilhelm von Hofmann, helping with laboratory work and research. In October 1851, he was promoted to senior assistant, a position he held until 1854.
Although Crookes respected Hofmann, he was more interested in other areas of science. One of his students, Reverend John Barlow, introduced him to scientists like George Gabriel Stokes and Michael Faraday. These connections helped Crookes develop his interest in optical physics, which Hofmann supported. By 1851, Crookes’s work in photography and optics led his father to build him a laboratory in the garden at home.
Crookes’s early research focused on new compounds of selenium, not organic chemistry. He published his first papers on this topic in 1851. In 1854, he worked with Manuel Johnson at the Radcliffe Observatory in Oxford, adapting wax paper photography to machines built by Francis Ronalds for recording weather data. In 1855, he became a chemistry lecturer at the Chester Diocesan Training College.
In April 1856, Crookes married Ellen, the daughter of William Humphrey of Darlington. Because staff at Chester had to be unmarried, he resigned his position. His father gave the couple a house at 15 Stanley Street, Brompton. Ellen’s mother lived with them for nearly forty years. William and Ellen had six sons and three daughters. Their first child, Alice Mary, remained unmarried for forty years, living with her parents and helping her father. Two of Crookes’s sons became engineers, and two became lawyers.
After marrying, Crookes worked as a photographic chemist in London to support his family. In 1859, he founded Chemical News, a science magazine he edited for many years. He published Michael Faraday’s lectures on natural forces and edited them into a book in 1860. Between 1864 and 1869, he also worked on the Quarterly Journal of Science. At times, he edited the Journal of the Photographic Society and Photographic News.
Crookes was skilled in experiments. He used a new method called spectral analysis, developed by Bunsen and Kirchhoff, to study chemical elements. His first major discovery was thallium, identified using flame spectroscopy. He found a bright green line in thallium’s spectrum and named the element after the Greek word thallós, meaning “green shoot or twig.” His findings were published on March 30, 1861.
Thallium was also discovered independently by French scientist Claude Auguste Lamy, who had access to more materials through his brother-in-law. Both scientists isolated thallium in 1862.
In 1863, Crookes was elected a fellow of the Royal Society. In 1871, he wrote a standard textbook on Select Methods in Chemical Analysis.
In 1866, a mineral containing copper, thallium, and silver was named crookesite in his honor.
Crookes invented the Crookes tube, a device used to study cathode rays. He published many papers on spectroscopy and researched various topics. His experiments with low-pressure gases showed that cathode rays (now known as streams of electrons) were emitted from the negative electrode. His work helped scientists understand plasma, which he called the fourth state of matter in 1879. He also created the spinthariscope, an early tool for studying nuclear radioactivity.
Crookes studied cathode rays, showing they traveled in straight lines, caused fluorescence, and produced heat. He believed they were made of ordinary particles, though later scientists like J. J. Thomson proved they were electrons. Crookes’s experiments laid the foundation for future discoveries in chemistry and physics.
Crookes’s interest in vacuum balances led him to discover the principle behind the Crookes radiometer, a device with black and polished vanes that rotate when exposed to light. He did not fully explain why this happened.
After 1880, Crookes lived at 7 Kensington Park Gardens in Notting Hill. His home included a large family and servants. His laboratory, considered the finest private lab in Britain, occupied an entire floor of the house. It had three connected rooms for chemistry, physics, and mechanical work, plus a library. He could afford the house and lab due to income from the National Guano Company and patents.
By 1880, Crookes employed a full-time scientific assistant (first Charles Gimingham, then James Gardiner). His daughter Alice helped with experiments, especially separating rare earth elements.
Spiritualism
Crookes became interested in spiritualism in the late 1860s, and was most involved around 1874–1875. Eric Deeson noted that Crookes's studies of the occult were connected to his scientific work on radiometry, as both involved finding new forces.
Crookes may have been influenced by the death of his younger brother, Philip, in 1867 at age 21 from yellow fever he contracted during an expedition to lay a telegraph cable between Cuba and Florida. In 1867, influenced by Cromwell Fleetwood Varley, Crookes attended a séance to try to contact his brother.
Between 1871 and 1874, Crookes studied the mediums Kate Fox, Florence Cook, and Daniel Dunglas Home. After his investigations, he believed the mediums could produce real paranormal events and communicate with spirits. Psychologists Leonard Zusne and Warren H. Jones described Crookes as easily convinced, as he accepted fraudulent mediums as genuine.
Anthropologist Edward Clodd noted that Crookes had poor eyesight, which may have contributed to his belief in spiritualist phenomena. He quoted William Ramsay as saying that Crookes was "so shortsighted that, despite his honesty, he cannot be trusted in what he claims to have seen." Biographer William Hodson Brock wrote that Crookes was "evidently short-sighted but did not wear glasses until the 1890s. Until then, he may have used a monocle or magnifying glass when needed. The impact of this on his spiritualist research remains unknown."
After studying reports about Florence Cook, science historian Sherrie Lynne Lyons wrote that the alleged spirit "Katie King" was sometimes Cook herself or an accomplice. Lyons noted, "Here was a man with a strong scientific reputation, who discovered a new element, but could not detect a real woman pretending to be a ghost." Cook was repeatedly exposed as a fraud, but she had been trained in séance techniques that tricked Crookes. Some researchers, like Trevor H. Hall, suspected Crookes had a personal relationship with Cook.
In experiments at Crookes's London home in February 1875, the medium Anna Eva Fay convinced Crookes she had real psychic abilities. Fay later admitted to the fraud and revealed her methods. Magician Harry Houdini suggested Crookes had been deceived. Physicist Victor Stenger wrote that the experiments were poorly controlled and that Crookes's desire to believe blinded him to the tricks used by the mediums.
In 1897, John Grier Hibben wrote that Crookes's idea of ether waves explaining telepathy was not a scientific hypothesis, as he provided no evidence to support it.
In 1916, William Hope tricked Crookes with a fake spirit photograph of his wife. Oliver Lodge noted that the image showed clear signs of double exposure, as Lady Crookes's picture was copied from a wedding anniversary photo. Despite this, Crookes remained a spiritualist and claimed the photo was real proof of spirit photography.
Physiologist Gordon Stein suggested that Crookes may have been too embarrassed to admit he was tricked by Florence Cook or that he conspired with her for personal reasons. He also claimed Crookes may have colluded with Anna Eva Fay. Stein noted that Hope had been exposed as a fraud before and that his tricks were conjuring techniques. Biographer William Brock wrote that Stein presented his case against Crookes and Hope clearly and logically.
Crookes joined the Society for Psychical Research and became its president in the 1890s. He also joined the Theosophical Society and The Ghost Club, of which he was president from 1907 to 1912. In 1890, he was initiated into the Hermetic Order of the Golden Dawn.