96 THE LIMITATIONS OF SCIENCE 



degrees Centigrade. Not to contradict known phe- 

 nomena, and to anticipate some unknown ones, is held 

 to be the justification of such hypotheses; by this 

 standard Descartes was successful as few others have 

 been. Yet, if we compare the splendid advances which 

 he made in science by his experimental discoveries and 

 his application of mathematics to physical laws, to the 

 mass of falsehood in his metaphysical schemes by 

 which he dominated science and which still flourish 

 in the metaphysical theories now in vogue, we can 

 hardly tell whether he has benefited or done harm to 

 science by his labors. Possibly no labor is too great, 

 if by it we arrive at ever so little truth, but no one can 

 believe that this medieval conception of light and heat 

 induced his successors to seek for a possible, but unex- 

 pected, contraction of water. Surely the converse is 

 the case and his metaphysical divination was purely 

 specious ; the phenomena were discovered without any 

 reference to his theory and probably without even a 

 knowledge of it, and now, if we wish, we may use them 

 as a buttress for Descartes's tottering edifice. 



The fourth and last book of the Principia is devoted 

 to an explanation of the natural phenomena of the 

 earth. At first the earth was a small stellar vortex, 

 composed of matter of the first kind only, and was one 

 of fourteen satellary nuclei located in our larger solar 

 vortex. Gradually the less subtile parts of its mass 

 attached themselves together and formed spots or 



