Manchester Memoirs^ Vol. xliii. (1899), No. 4. 19 



by polymerisation ; and the low boiling point of argon, 

 which has an atomic weight somewhat higher than that 

 of chlorine, and which might be expected, therefore, to 

 boil at a higher temperature than chlorine, is without 

 doubt due to its mono-atomic nature. The boiling point 

 of neon lies below the lowest temperature which can be 

 reached by reducing the pressure on boiling air, a tempera- 

 ture which has been estimated as — 215'^C. And the 

 boiling point of xenon is so high, that at the temperature of 

 boiling air, its vapour pressure is only a few millimetres 

 of mercury. 



Further research will solve these problems, which are 

 among those which suggest themselves in connection with 

 the newly discovered elements of the air. 



