68 PROGRESS OF SCIENCE IN THE CENTURY. 



Over and over again in the course of the history of 

 science we find illustrations of the long gestation of 

 scientific truth. Minerva-like birth is rare. " Dis- 

 coveries which proved all important in secondary re- 

 sults do not burst forth full grown; they are, so to 

 say, the crown of a structure raised painfully and 

 noiselessly by men indifferent to this world's affairs, 

 caring little for fame and even less for wealth. 

 Facts are gathered, principles are discovered, each 

 falling into its own place, until at last the brilliant 

 crown shines out, and the world thinks it sees a 

 miracle." * But it was after waiting and working 

 for almost a score of years that Darwin published his 

 theory of natural selection. 



Another good illustration of the gradual emergence 

 of an important conclusion is to be found in the 

 history of the kinetic theory of gases. We usually, 

 and rightly, associate this conception with the names 

 of Joule and Clausius, and fix the date about 1857, 

 but " the researches of Paul du Bois-Reymond and 

 others have unearthed a whole list of authors who, in 

 more or less definite ways, had resorted to the hypo- 

 thesis of a rectilinear translatory motion of the 

 molecules in order to explain the phenomena of pres- 

 sure and other properties of gases. Among these 

 Daniel Bernouilli (in his Hydrodynamica, 1738), 

 seems to have expressed the clearest views, and he is 

 usually now named as the " father of the hypoth- 

 esis." f 



While then we hold firmly that science is for life 

 and not life for science, we protest against a narrow 

 rendering of the words " for life." The practical 

 man's impatient "What's the use of it ? " often reveals 



* J. J. Stevenson, Rep. Smithsonian Inst., for 1897, p. 325. 

 t J. T. Merz, History, 1896, p. 433. 



