PHYSICAL CONTEMPLATION OF THE UNIVERSE. 467 



light of self-luminous bodies, or in other words determin- 

 ing whether solar light be radiated from a solid mass or from 

 a gaseous envelope. The enumeration of the experiments 

 which, since Huygens 1 time, have gradually led to Arago's 

 discovery of coloured polarisation must be reserved for the 

 history of optics. The consideration of the development of 

 the principles, in accordance with which variously formed 

 plants admit of being classified in families, falls, in like man- 

 ner, within the domain of the history of phytognosy, or botany; 

 whilst the geography of plants, or a study of the local and 

 climatic distribution of vegetation over the whole earth alike 

 over the solid portions and in the basins of the sea consti- 

 tutes an important section in the history of the physical con- 

 templation of the universe. 



The* intellectual consideration of that which has led man to 

 an insight into the unity of nature is, as we have already 

 observed, as little entitled to the appellation of the complete 

 history of the cultivation of mankind as to that of a history^, 

 of the natural sciences. An insight into the connection of 

 the vital forces of the universe must certainly be regarded as 

 the noblest fruit of human civilisation, and as the tendency to 

 arrive at the highest point to which the most perfect develop- 

 ment of the intellect can attain; but the subject at present 

 under consideration must still constitute only a part of the his- 

 tory of human civilisation, embracing all that has been attained 

 by the advance of different nations in the pursuit of every 

 branch of mental and moral culture. By assuming a more 

 limited physical point of view, we necessarily become restricted 

 to one section of the history of human knowledge, and our 

 attention is specially directed to the relation existing between 

 the knowledge that has been gradually acquired and the whole 

 extent of the domain of nature; and we dwell less on the 

 extension of separate branches of science than on the results 

 capable of generalisation, and the material aids contributed by 

 different ages towards a more accurate observation of nature.^ 



We must, above all, distinguish carefully between an early 

 presentiment of knowledge, and knowledge itself. With the 

 increasing cultivation of the human race, much has passed 

 from the former to the latter, and by this transition the 

 history of discovery has been rendered indistinct. An intel- 

 lectual and ideal combination of the facts already established 



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