Every schoolboy today knows that Boyle and Mariotte are two different physicists, while Gay-Lussac is one person. Today we celebrate the birthday of a one, but a very prominent scientist. It wouldn’t be an exaggeration to say that he worked for two: a single Joseph Louis Gay-Lussac discovered two gas laws named after him, discovered boron, prepared hydrogen cyanide, improved the methods of chemical analysis, and the production process of sulfuric acid. Twice did he go up on hot air balloons for scientific purposes: and during the second flight, climbed to an altitude of over 7 kilometers. He also gave a name to chlorine, invented the barometer, hydrometer, alcohol meter, various thermometers, and patented the production process of stearin candles. Wouldn’t one dance for joy? And he danced: more than once, his students saw dancing in the lab after a successful experiment.