THE ASTRONOMICAL VIEW OF NATURE. 341 



a century of confirming thought, observation, and calcula- 

 tion an adopted axiom, and the accepted formula of all 

 physical explanations. For a time, indeed, the exact 

 formula of gravitation seemed liable to some correction, 

 but gradually the apparent anomalies disappeared, and 

 even in our century none of the many attempts to modify 

 the gravitation formula, to look upon it as merely an ap- 

 proximation, or to go behind it and find some more general 

 relation from which it could be deduced, have been gen- 

 erally useful or acceptable.-^ It still stands there as the 

 only universally accepted mathematical expression which 

 corresponds to a general physical property of natural 

 objects. 



Two different lines of thought combined to give the 

 formula of Newton a still wider importance than its 

 author primarily intended, or than it has been found 

 possible to maintain in the course of further inquiry. The 

 first was the ancient philosophical idea of attraction, which, 

 without being mathematically defined and practically use- 

 ful, had nevertheless, from the dawn of Greek speculation 



of that tendency, are now suffici- these diflerent attempts will be 



eutly known by observations and found in the writings of C. Isen- 



experinients. If this or any other krahe, ' Das liathsel von der 



learned author can by the laws of , Schwerkraft,' Braunschweig, 1879; 



mechanism explain these phenom- i " Euler's Theorie von der Ursache 



ena, he will not only not be con- der Gravitation," in 'Zeitschrift fiir 



tradicted, but will, moreover, have I Mathematik und Physik,' V(j1. xxvi. ; 



the abundant thanks of the learned i ' Ueber die Fernkraft,' Leipzig, 



world. But in the meantime, to 1 1889; "Ueber die Zuriickfiihrung 



compare gravitation, which is a phe- der Schwere auf Absorption," in 



nomenon or actual matter of fact, ' Abhandlungen zur Gescliichte der 



with Epicurus' declination of atoms Mathematik,' vol. vi., Leipzig, Teub- 



seems to be a very extraordinary ner, 1892. See also as bearing on 



method of reasoning" (118-124, this subject, Paul du Bois-Reymond, 



Leibniz's ' Philosophische Schrif- 'Ueber die Grundlagen der Erkennt- 



ten,' by Gerhardt, Berlin, 1890, vol. niss in den exacten Wissenschaft- 



vii. p. 439 sq.) en,' Tubingen, 1890. 

 ^ A very complete account of 



