78 INTRODUCTION TO SCIENCE 



interpolations, in which every event is deter- 

 mined by antecedent events. 



Clerk Maxwell discussed the Uniformity of 

 Nature in his famous Discourse on Molecules 

 (1873). 



"In the heavens we discover by their light, 

 and by then* light alone, stars so distant from 

 each other that no material thing can ever have 

 passed from one to another; and yet this light, 

 which is to us the sole evidence of the existence 

 of these distant worlds, tells us also that each 

 of them is built up of molecules of the same 

 kinds as those which we find on earth. A mole- 

 cule of hydrogen, for example, whether in Sirius 

 or in Arcturus, executes its vibrations in pre- 

 cisely the same time. 



"Natural causes, as we know, are at work 

 which tend to modify, if they do not at length 

 destroy, all the arrangements and dimensions 

 of the earth and the whole solar system. But 

 though in the course of ages catastrophes have 

 occurred and may yet occur in the heavens, 

 though ancient systems may be dissolved and 

 new systems evolved out of their ruins, the mole- 

 cules out of which these systems are built the 

 foundation-stones of the material universe re- 

 main unbroken and unworn. They continue this 

 day as they were created perfect in number and 

 measure and weight. . . ." 



