II THE PROGRESS OF SCIENCE 65 



ment, and speculation have gone hand in hand ; 

 and, whenever science has halted or strayed from 

 the right path, it has been, either because its 

 votaries have been content with mere unverified 

 or unverifiable speculation (and this is the com- 

 monest case, because observation and experiment 

 are hard work, while speculation is amusing) ; or 

 it has been, because the accumulation of details of 

 observation has for a time excluded speculation. 



The progress of physical science, since the 

 revival of learning, is largely due to the fact 

 that men have gradually learned to lay aside 

 the consideration of unverifiable hypotheses ; to 

 guide observation and experiment by verifiable 

 hypotheses ; and to consider the latter, not as 

 ideal truths, the real entities of an intelligible 

 world behind phenomena, but as a symbolical 

 language, by the aid of which Nature can be in- 

 terpreted in terms apprehensible by our intellects. 

 And if physical science, during the last fifty years, 

 has attained dimensions beyond all former pre- 

 cedent, and can exhibit achievements of greater 

 importance than any former such period can show, 

 it is because able men, animated by the true 

 scientific spirit, carefully trained in the method of 

 science, and having at their disposal immensely 

 improved appliances, have devoted themselves to 

 the enlargement of the boundaries of natural 

 knowledge in greater number than during any 

 previous half-century of the world's history. 



VOL. I. F 



