PROFESSOR WILLIAM RAMSAY. 3 



nesium. The result of his experiments was the discovery 

 of a new gaseous constituent of the air, the same gas having 

 also been isolated by Lord Rayleigh at the same time by 

 causing the atmospheric nitrogen to combine with oxygen 

 by the passage of electric sparks. The discovery had 

 oeen to a certain extent anticipated by Cavendish, who 

 noticed that when atmospheric nitrogen was sparked with 

 oxygen a small residue — rather less then 1 per cent. — was 

 left, but he was unable to ascertain the nature of the sub- 

 stance, and the observation was entirely overlooked until 

 after the researches of Lord Rayleigh and Professor Ramsay 

 had been completed. On account of its inertness the new 

 gas has been named " Argon " by the discoverers. The gas 

 has been liquefied and the boiling-point and critical tempera- 

 ture and pressure of the liquid determined by Olszewski. 

 The remarkable observation has been made by Professor 

 Ramsay that the ratio of the specific heat of argon at 

 constant pressure to that at constant volume possesses 

 almost exactly the theoretical value 1"66 for a monatomic 

 gas, as is also the case with mercury vapour. As the density 

 of argon compared with hydrogen is about 20, it would appear 

 that the atomic weight — if the gas is elementary — must be 

 nearly 40, and a difficulty thus arises in placing the element 

 in the periodic table of the elements. The solution of this 

 problem will be of great theoretical interest. 



Shortly after the discovery of argon, Dr. Ramsay was led 

 to examine the gas evolved by treating certain minerals 

 containing uranium, notably cleveite, with sulphuric acid. 

 This gas had been previously obtained by Hillebrand, who 

 considered it to consist of nitrogen. Professor Ramsay found, 

 however, that when an electric discharge is passed through 

 the gas under low pressures, a bright yellow light is emitted, 

 and a spectroscopic examination of the light showed the 



