VII 

 SOME UNSOLVED SCIENTIFIC PROBLEMS 



TN recent chapters we have witnessed a marvellous 

 1 development in many branches of pure science. In 

 viewing so wonderfully diversified a field, it has of 

 course been impossible to dwell upon details, or even 

 to glance at every minor discovery. At best one could 

 but summarize the broad sweep of progress somewhat 

 as a battle might be described by a distant eye-witness, 

 telling of the general direction of action, of the move- 

 ments of large masses, the names of leaders of brigades 

 and divisions, but necessarily ignoring the lesser fluct- 

 uations of advance or recession and the individual 

 gallantry of the rank and file. In particular, interest 

 has centred upon the storming of the various special 

 strongholds of ignorant or prejudiced opposition, which 

 at last have been triumphantly occupied by the band 

 of progress. In each case where such a stronghold has 

 fallen, the victory has been achieved solely through 

 the destructive agency of newly discovered or newly 

 marshalled facts the only weapons which the warrior 

 of science seeks or cares for. Facts must be mar- 

 shalled, of course, about the guidon of a hypothesis, but 

 that guidon can lead on to victory only when the facts 

 themselves support it. Once planted victoriously on 

 the conquered ramparts the hypothesis becomes a 

 theory a generalization of science marking a fresh 



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