LECTURES. 



41 



discovered, and the properties of these unknown elements he had 

 the courage to foretell. 



The impulse thus given to fresh research resulted in the 

 discovery of Gallium, Scandium, etc., every one of the newly 

 discovered elements entirely fulfilling the prediction made about it. 



As for the future, a few rare elements might be expected to 

 turn up in rare minerals, but beyond this little hope could be 

 entertained of discovery in this direction, unless indeed some new 

 instrument or new method of decomposition should enable chemists 

 to decompose the present elements into still simpler ones. 



It is easier to imagine therefore than describe the excitement 

 felt among members of the British Association at the Oxford Meet- 

 ing in August, 1894, when Lord Rayieigh and Professor Ramsay 

 were rumoured to have found a new element independently of any 

 of the means above mentioned. The interest was kept up by the 

 statement that it occurred in large quantities in the free state in the 

 very air we breathed. 



At first the discoverers were very guarded in their language, 

 and did not definitely call the body a new element, and five 

 months elapsed before anything more than the bare announcement 

 was heard from the discoverers, and during this time a large 

 amount of scepticism was expressed. 



In the first place the composition of the air had so frequently 

 been determined by experimenters of undoubted ability that it was 

 customary to write down its composition by volume to five places 

 of decimals. An error in the third or fourth decimal place was 

 within the bounds of possibility, but scarcely one in the units— the 

 amount hinted at by Lord Rayieigh. 



In the second place, Professor Dewar had recently liquified 

 air, and had not noticed any new constituent as one might have 

 expected that he would. 



All these doubts were finally laid to rest at the meeting of the 

 Royal Society on January 31st, 1895, when the original discovery 

 was confirmed and a full account of the experimental details, 

 needed to establish it, given. 



Omitting accidental impurities, the proportion of the gases in 

 the air used to be given as follows : — 



Nitrogen 77-90600 



Oxygen 20-65940 



Moisture 1-40000 



Carbon dioxide '03360 



