Ramsay was proud of the fact that his ancestors included several scientists, and he moved easily into science at Glasgow and then into chemistry with Fittig at Tübingen. In 1880, at Bristol, he began to make exact measurements of gas densities, and became an expert glassblower. In 1887 he moved to London and in 1894 began the work that made him famous. Rayleigh had shown that nitrogen from the air is 0.5% denser than nitrogen made chemically. Ramsay thought that this might be due to a previously unknown heavier gas in the air, and he set to work to find it. He sparked dry air to remove oxygen and then passed the nitrogen repeatedly over hot magnesium, when most of the gas was slowly absorbed: 3Mg + N2→Mg3N2. He was left with a denser, monatomic gas: an inert new element, which was named argon and which makes up less than 1% of the air. Looking for it elsewhere, Ramsay found another new gas in the mineral cleveite, whose spectrum showed Crookes that it was helium, previously observed only in the Sun. Ramsay went on to examine air for traces of other new inert gases, and by distilling liquid air he discovered three more: krypton, xenon and neon. Ramsay proposed that the five new gases formed a new group of ‘zero-valent’ elements in the periodic table. In 1910 he found the sixth of these gases, radon, which is formed with helium by the radioactive decay of the metal radium. The group are now known as the noble gases.