54 PROGRESS OF SCIENCE 



generally thought that our power to discover new 

 experimental facts was practically exhausted/ The 

 Earl of Rosse, in his presidential address in 1843, at 

 once foreshadowed this attitude of mind and offered 

 an explanation and a corrective : ' Each successive 

 discovery, as it brings us nearer to first principles, 

 opens out to our view a new and more splendid 

 prospect, and the mind, led away by its charms, is 

 carried beyond and far above the petty and ephemeral 

 contests of life ; but the more rapid the discoveries 

 are, the more powerful the charm, and therefore 

 great is the motive for exertion ; and in labouring 

 in this cause there is this gratifying reflection, that 

 our labours cannot injure our successors, for the 

 region of discovery is rich beyond the powers of 

 conception/ A new era in physical research opened 

 when Rayleigh, observing two different densities 

 for nitrogen obtained by two different methods, was 

 led, in conjunction with Sir William Ramsay, to the 

 discovery of a new gas in the atmosphere, which was 

 announced at the meeting of the British Association 

 in 1894, and was named argon. Ramsay (1852-1916) 

 proceeded to the brilliant researches by which he 

 isolated further new elements. Again, experiments 

 on the discharge of electricity through gases, carried 

 on by Crookes and others, led up to the conception 

 of the atomic constitution of electricity, and Sir 

 J. J. Thomson demonstrated the existence of the 

 electron, of smaller mass than the chemical atom, as 

 the carrier of negative electricity. This discovery, 

 again, was proclaimed at a British Association 

 meeting at Dover in 1899. 



The occasion of this announcement by Thomson 

 ' On the Existence of Masses smaller than the Atoms ' 



