60 DISCOVERY CH. 



of mind which seemed to be of special and extreme advantage 

 in leading him to make discoveries. It was the power of never 

 letting exceptions pass unnoticed. 



Writing to Nature of September 29, 1892, Lord Rayleigh 

 said, " I am much puzzled by some recent results as to 

 the density of nitrogen, and shall be obliged if any of your 

 chemical readers can offer suggestions as to the cause. 

 According to two methods of preparation I obtain quite 

 distinct values." It appeared from Lord Rayleigh's 

 observations that while nitrogen derived from the air 

 weighed 2 '3 102 grammes under standard conditions in 

 a certain globe, nitrogen obtained as a chemical product 

 from other sources than the air weighed 2*2990 grammes 

 under exactly the same conditions. These values do 

 not, of course, represent two experiments only, but are 

 averages of many weighings carried out with the greatest 

 possible care and precision. The difference between the 

 two values is 11 milligrammes, or one-half per cent. 



Expressed in British weight, the difference which 

 puzzled Lord Rayleigh was about one-sixth of a grain. 

 Small as this difference was, it exceeded the possible 

 errors of the experiments, and gave rise to the con- 

 clusions that the natural nitrogen from the air was 

 different in character from nitrogen manufactured from 

 chemical substances. Later investigations with Sir 

 William Ramsay led to the discovery of a new gas 

 to which the name Argon was given in air ; and this 

 gas, which is nearly half as dense again as nitrogen, 

 caused the discrepancy noticed by Lord Rayleigh. 



Accurate and minute measurement seems to the non-scientific 

 imagination a less lofty and dignified work than looking for 

 something new. Yet nearly all the grandest discoveries of science 

 have been but the rewards of accurate measurement and patient, 

 long-continued labour in the minute sifting of numerical results. 

 Lord Kelvin. 



