Xll INTRODUCTION. 



Newton, struck away these crude devices, and substituted the action 

 of a universal immaterial force. The course of astronomic science 

 has thus been on a vast scale to withdraw attention from the mate- 

 rial and sensible, and to fix it upon the invisible and supersensuous. 

 It has shown that a pure principle forms the immaterial foundation 

 of the universe. From the baldest materiality we rise at last to a 

 truth of the spiritual world, of so exalted an order that it has been 

 said Ho connect the mind of man with the Spirit of God.' 



The tendency thus illustrated by astronomy is characteristic in 

 a marked degree of all modern science. Scientific inquiries are 

 becoming less and less questions of matter, and more and more 

 questions of force ; material ideas are giving place to dynamical 

 ideas. "While the great agencies of change with which it is the 

 business of science to deal heat, light, electricity, magnetism, and 

 affinity, have been formerly regarded as kinds of matter ' impon- 

 derable elements,' in distinction from other material elements, 

 these notions must now be regarded as outgrown and abandoned, 

 and in their place we have an order of purely immaterial forces. 



Toward the close of the last century the human mind reached 

 the great principle of the indestructiblity of matter. "What the 

 intellectual activity of ages had failed to establish by all the re- 

 sources of reasoning and philosophy, was accomplished by the in- 

 vention of a mechanical implement, the balance of Lavoisier. 

 When nature was tested in the chemist's scale-pan, it was first 

 found that never an atom is created or destroyed ; that though 

 matter changes form with protean facility, traversing a thousand 

 cycles of change, vanishing and reappearing incessantly, yet it 

 never wears out or lapses into nothing. 



The present age will be memorable in the history of science for 

 having demonstrated that the same great principle applies also to 

 forces, and for the establishment of a new philosophy concerning 

 their nature and relations. Heat, light, electricity, and magnetism 

 are now no longer regarded as substantive and independent exist- 

 encessubtile fluids with peculiar properties, but simply as modes 



