John William Strutt Rayleigh, the great scientist, who lived in the years 1842-1919, default with many problems of physics. Among the others, he tried to evaluate Avogadro's constant; he estimated quantities of the molecules of different compounds; he searched the occurrence of the surface tension, what let him evaluate the forces acted between the particles. In the year 1894 together with William Ramsay he discovered the first of the helium-group gasses - argon.