46 C.C. NATURAL HISTORY SOCIETY, 



been mistaken for Argon. Thinking that this might present an 

 easy method for the preparation of this gas he repeated the experi- 

 ment. Judge then of his surprise when on examining the spectrum 

 of the gas he found neither Nitrogen nor Argon Unes, but a very 

 prominent bright yellow line. Professor Lockyer on being in- 

 formed of this result was soon able to confirm the fact that the 

 element Helium, which had been teasing astronomers for over a 

 quarter of a century, was at last run to earth. 



Several other minerals were found to evolve the gas, Clevite 

 being the most important. Thus the source of most, but not of 

 all, of the strange lines in the sun's light was explained. The 

 remaining ones are doubtless due to some other body still 

 unknown. 



The properties of Helium bear a very marked resemblance to 

 those of Argon. It unites with no other substance and seems to 

 be merely included in the minerals from which it is obtained. Its 

 density is 2, and therefore, after Hydrogen, it is the lightest known 

 gas. 



Like Argon, its molecule appears to contain only one atom. 

 Like Hydrogen it is exceptional among gases in being a good 

 conductor of Electricity. Careful observations on its spectrum, 

 points to its being a mixture of two gases. The same was said of 

 Argon, but unhke that gas the latest experiments of Professor 

 Ramsay have shown that Helium is divisible into two portions by 

 diffusion, the one gas having a density of 2*1 and the other i'5. 

 These might naturally be expected to exhibit different spectra, but 

 as far as is known at present, they do not. Hence we have the 

 extraordinary phenomenon of the same elenient apparently possess- 

 ing different atomic weights. It rests with the future to either 

 confirm or deny the accuracy of these experiments. If they are 

 correct then the atomic theory will stand in need of considerable 

 alteration. 



