THK 



SCIENCE 



II 



Hi-it her an ellipse nor any other simple curve, but 

 an immensely complicated undulating line. It 

 may fairly be doubted whether any generalisation, 

 or hypothesis, based upon physical data is ab- 

 solutely true, in the sense that a mathematical 

 proposition is so ; but, if its errors can become 

 apparent only outside the limits of practicable ob- 

 servation, it may be just as usefully adopted for 

 one of the symbols of that algebra by which we 

 interpret Nature, as if it were absolutely true. 



The development of every branch of phy 

 knowledge presents three stages, which, in their 

 logical relation, are successive. The first is the 

 determination of the sensible character and order 

 of the phenomena. This is Natural Histoi-y, in 

 the original sense of the term, and here nothing 

 but observation and experiment avail us. The. I 

 second is the determination of the constant 

 relations of the phenomena thus defined, and 

 their expression in rules or laws. The third is i 

 the explication of these particular laws by deduc- 

 tion from the most general laws of matter and 

 motion. The last two stages constitut' 

 Philosophy in its original sense. In this region, j 

 the invention of verifiable hypotheses is not only 

 permissible, but is one of the conditions 

 progress. 



Historically, no branch of science has followe 

 this order of growth; but, from the dawn of 

 knowledge to the .present day, observation, experi-j 



