106 COSMOS. 



PART II. 



HISTORY OF THE PHYSICAL CONTEMPLATION OF THE UNIVERSE. 

 PRINCIPAL CAUSES OF THE GRADUAL DEVELOPMENT AND EXTEN- 

 SION OF THE IDEA OF THE COSMOS AS A NATURAL UNITY. 



THE history of the physical contemplation of the universe 

 is the history of the recognition of the unity of nature, the rep- 

 resentation of the efforts made by man to comprehend the 

 combined action of natural forces on the earth and in the re- 

 gions of space, and hence it designates the epochs of advance- 

 ment in the generalization of views, being a portion of the 

 history of our world of thought, in as far as it refers to objects 

 manifested by the senses, to the form of conglomerated mat- 

 ter, and the forces inherent in it. 



In the section of the first portion of this work, relating to 

 the limitation and scientific treatment of a physical description 

 of the universe, I hope I may have succeeded in developing 

 with clearness the relation existing between the separate nat- 

 ural sciences and the description of the universe (the science 

 of the Cosmos), and the manner in which this science simply 

 draws from these various branches of study the materials for 

 its scientific foundation. The history of the knowledge of the 

 universe, of which I here present the leading ideas, and which, 

 for the sake of brevity, I name either simply the history of the 

 Cosmos, or the history of the physical contemplation of the uni- 

 verse, must not, therefore, be confounded with the history of 

 the natural sciences, as given in many of our leading element- 

 ary works on physics and physiology, or on the morphology 

 of plants and animals. 



In order to give some idea of what has been collected at 

 separate epochs under this point of view, it appears most de- 

 sirable to adduce separate instances illustrative of the subjects 

 which must either be treated of or discarded in the succeed- 

 ing portions of this work. The discoveries of the compound 

 microscope, of the telescope, and of colored polarization, belong 

 to the history of the Cosmos, since they have afforded the 

 means of discovering that which is common to all organisms ; 

 of penetrating into the remotest regions of space ; of distin- 

 guishing between reflected or borrowed light, and the light of 

 Belf-luminous bodies, or, in other words, determining whether 



