COMPARISON WITH OTHER CENTURIES. 155 



OF ALL PRECEDING AGES. 



6. Arabic Numerals. 



7. Alphabetical Writing. 



8. Modern Chemistry Founded. 



9. Electric science Founded. 



10. Gravitation Established. 



11. Kepler's Laws. 



12. The Differential Calculus. 



13. The Circulation of the 



Blood. 



14. Light proved to have Finite 



Velocity. 



15. The Development of Geo- 



metry. 



OF THE NINETEENTH 

 CENTURY. 



7. Electric Lighting. 



8. Photography. 



9. The Phonograph. 



10. Rontgen Rays. 



11. Spectrum Analysis. 



12. Anaesthetics. 



13. Antiseptic Surgery. 



14. Conservation of Energy. 



15. Molecular Theory of Gases. 



16. Velocity of Light Directly 



Measured, and Earth's 

 Rotation Experimentally 

 Shown. 



17. The Uses of Dust 



18. Chemistry, Delinite Pro- 



portions. 



19. Meteors and the Meteoritic 



Theory. 



20. The Glacial Epoch. 



21. The Antiquity of Man. 



22. Organic Evolution Estab- 



lished. 



23. Cell Theory and Embry- 



ology. 



24. Germ Theory of Disease, 



and the Function of the 

 Leucocytes. 



Of course these numbers are not absolute. Either 

 series may be increased or diminished by taking account 

 of other discoveries as of equal importance, or by strik- 

 ing out some which may be considered as below the 

 grade of an important or epoch-making step in science or 

 civilization. But the difference between the two lists 

 is so large that probably no competent judge would 

 bring them to an equality. Again, it is noteworthy that 

 nothing like a regular gradation is perceptible during 



