252 PERSONAL PREPARATION FOR RESEARCH. 



Jevons, ' genius united to extensive knowledge, cultivated 

 powers, and indomitable Industry, constitute the charac- 

 teristics of the great discoverer.' c The mind of the great 

 discoverer must combine almost contradictory attributes. 

 He must be fertile in theories and hypotheses, and yet full 

 of facts and precise results of experience. He must enter- 

 tain the feeblest analogies and the merest guesses at truth, 

 and yet he must hold them as worthless till they are veri- 

 fied in experiment. When there are any grounds of pro- 

 bability he must hold tenaciously to an old opinion, and 

 yet he must be prepared at any moment to relinquish it 

 when a single clear contradictory fact is encountered ' ; l 

 and this is perhaps as accurate an ideal as can be briefly 

 given. 



' Great men of science have for the most part been 

 patient, laborious, cheerful-minded men. Such were 

 Galileo, Descartes, Newton, and Laplace. Euler, the 

 mathematician, one of the greatest of natural philosophers, 

 was a distinguished instance. Towards the close of his 

 life he became completely blind, but he went on writing 

 as cheerfully as before, supplying the want of sight by 

 various ingenious mechanical devices, and by the increased 

 cultivation of his memory, which became exceedingly 

 tenacious.' ' One of the sorest trials of a man's temper 

 and patience was that which befell Abauzit, the natural 

 philosopher, while residing at Geneva, resembling in 

 many respects a similar calamity which occurred to 

 Newton, and which he bore with equal resignation. 

 Amongst other things, Abauzit devoted much study to the 

 barometer and its variations, with the object of deducing 

 the general laws which regulated atmospheric pressure. 

 During twenty-seven years he made numerous observations 



1 Principles of Science, vol. ii. pp. 166, 240. 



