104 HISTORY OF THE PHYSICAL 



tient imagination, the all-animating activity of spirit, which 

 lived in Plato, in Columbus, and in Kepler, must not be 

 reproached as if it had effected nothing in the domain of 

 science, or as if it tended necessarily to withdraw the mind 

 from the investigation of the actual. 



Since we have defined the subject before us as the history 

 of nature as a whole, or of unity in the phenomena and con- 

 currence in the action of the forces of the universe, our method 

 of proceeding must be to select for our notice those subjects 

 by which the idea of the unity of phsenomeua has been gradu- 

 ally developed. We distinguish in this respect, 1, the efforts 

 of reason to attain the knowledge of natural laws by athought- 

 ful consideration of natural phenomena ; 2, events in the 

 world's history which have suddenly enlarged the horizon 

 of observation ; 3, the discovery of new means of perception 

 through the senses, whereby observations are varied, multi- 

 plied, and rendered more accurate, and men are brought 

 into closer communication both with terrestrial objects and 

 with the most distant regions of space. This threefold 

 view must be our guide in determining the principal epochs 

 of the history of the science of the Cosmos. For the sake 

 of illustrating what has been said, we will again adduce 

 particular instances, characteristic of the different means by 

 which men have gradually arrived at the intellectual posses- 

 sion of a large part of the material universe. I take, there- 

 fore, examples of " the enlarged knowledge of nature," of 

 "great events/' and of the " invention or discovery of 

 new organs." 



The "knowledge of nature" in the oldest Greek physics, 

 was derived more from inward contemplation and from the 

 depths of the mind, than from the observation of phaeno- 



