NATURAL SCIENCE IN THE NINETEENTH CENTURY 367 



The American Revolution was likewise an uprising against 

 long established custom and authority, and accordingly contrib- 

 uted to the doubts and questionings of the time, while the 

 Industrial Revolution, by fundamental and world-wide changes, 

 such as the introduction of machinery and the factory system, 

 and by its tendency to concentrate and urbanize populations 

 previously rural and segregated, facilitated intellectual contact, 

 promoted discussion, and aroused and excited inquiry and in- 

 vestigation. 



THE SCIENTIFIC REVOLUTION. The most brilliant single 

 achievement of nineteenth century science was the detection by 

 Adams and Leverrier of the presence in our solar system of Nep- 

 tune, a new and hitherto unknown planet. But the most revolu- 

 tionary achievement, and probably the most far-reaching, was the 

 assembling and formulation of convincing evidence in favor of 

 organic evolution, i.e. of the gradual development, rather than 

 the sudden creation, of living things. It is difficult to-day to 

 realize the commotion into which the intellectual world was 

 thrown at the middle of the nineteenth century when a new and 

 promising solution of the long-standing problem of the origin of 

 the different kinds (species) of plants and animals by means of 

 natural rather than supernatural law, was propounded by Darwin 

 and Wallace. And while the last half of the eighteenth cen- 

 tury was the period of great political and social revolutions, 

 the French, the American, and the Industrial, the last half 

 of the nineteenth century experienced, in its acceptance of a new 

 cosmogony, a fourth, even more profound and momentous, the 

 Scientific Revolution. The discovery of Neptune was a triumph 

 of mathematics and astronomy, the establishment of the theory 

 of organic evolution, a triumph of biology. The discovery of 

 Adams and Leverrier was immediately accepted and everywhere 

 applauded, but the ideas broached by Darwin and his collabo- 

 rators encountered widespread and powerful opposition, and were 

 accepted only tardily and reluctantly. 



INFLUENCE OF THE RAPID INCREASE OF KNOWLEDGE. The 

 invention of printing, the discovery of the new world, and the works 



