Sir William Crookes (; 17 June 1832 – 4 April 1919) was a British chemist and physicist who attended the Royal College of Chemistry, now part of Imperial College London, and worked on spectroscopy. He was a pioneer of vacuum tubes, inventing the Crookes tube which was made in 1875. This was a foundational discovery that eventually changed the whole of chemistry and physics. He is credited with discovering the element thallium, announced in 1861, with the help of spectroscopy. He was also the first to describe the spectrum of terrestrial helium, in 1865. Crookes was the inventor of the Crookes radiometer but did not discern the true explanation of the phenomenon he detected. Crookes also invented a 100% ultraviolet blocking sunglass lens. For a time, he was interested in spiritualism and became president of the Society for Psychical Research. Biography Crookes' life was one of unbroken scientific activity that extended over sixty-seven years. He was considered remarkable for his industriousness and for his intellectual qualities. His experiments in chemistry and physics were known for the originality of their design, and he is considered a "superb experimentalist". His interests, ranging over pure and applied science, economic and practical problems, and psychic research, made him a well-known personality and earned him a substantial income. He received many public and academic honours. Early years William Crookes was born in London in 1832, the eldest of eight surviving children (eight others died young) of Joseph Crookes (1792-1889), a wealthy tailor and real estate investor of north-country origin, and his second wife, Mary (née Scott; 1806-1884). Joseph Crookes's father, William (1734-1814), was also a tailor, and his grandfather, John Crookes (b. 1660), had been Mayor of Hartlepool, County Durham on three occasions. Joseph Crookes had had five children with his first wife; two sons from that marriage, Joseph and Alfred, took over the tailoring business, leaving William free to choose his own path. In 1848, at age 16, Crookes entered the Royal College of Chemistry (now the Imperial College chemistry department) to study organic chemistry. Crookes lived with his parents 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's tuition and had to provide his own apparatus and some of the more expensive chemicals. At the end of his first year, Crookes won the Ashburton scholarship which covered