Which noble gas was discovered by Sir William Ramsay and Lord Rayleigh in August 13th, 1894?

Sir William Ramsay (2 October 1852- 23 July 1916) was a Scottish chemist. John William Strutt 3rd Baron Rayleigh (12 November 1842- 30 June 1919) was a British physicist. Ramsay and Rayleigh discovered the element Argon (Ar) in 1894. In 1904, they got the Nobel Prize in chemistry (Ramsay) and in physics (Rayleigh) for their discovery of Ar. Rayleigh first discovered the element during his attempts to determine more reliable atomic weights by precise density measurements on gases. He found nitrogen produced from ammonia was 0.5% lighter than from the atmosphere. Ramsay collected a pure sample of Ar and removed Rayleigh's difficulties. Ramsay and Rayleigh concluded the presence of 'argon' in the air. It was given the name from the Greek word 'argos', meaning 'inert'. Ramsay discovered afterwards the other inert gases. Argon makes up 0.93% of the earth's atmosphere. It is frequently used when an inert atmosphere is needed.