X INTRODUCTION 



men. We are beginning dimly to perceive that 

 the change produced by the study of science upon 

 the mind of man is hardly less great than the 

 change which that knowledge produces in his 

 power over nature. 



There was a time when men crouched in abject 

 terror of nature ; they trembled at the sound of 

 thunder ; they fell on their knees in the presence 

 of an eclipse ; a hurricane was the breath of an 

 evil spirit, and an epidemic the expression of the 

 wrath of an offended deity. Nature was an 

 enemy ; her powers were wielded by demons, to 

 make the brief and wretched lives of men briefer 

 and more miserable still. Ignorance of nature and 

 the wildest and most fantastic superstitions went 

 hand in hand. The inability to use natural forces 

 involved the inability to think clearly. The in- 

 ability to command nature by obeying her, in- 

 volved the inability to understand man's relation 

 to her. He who should stand erect in her pres- 

 ence, and, through penetration of her secrets, com- 

 mand her to do his bidding, crouches in terror 

 before her, and thinks of himself as her victim 

 and toy, and plaything, whenever he fails to under- 

 stand her. It is as though our beneficent teacher, 

 nature, would beguile us into getting the training 



