THE ASTEONOMICAL 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. 1 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- 

 ently known by observations and 

 experiments. If this or any other 

 learned author can by the laws of 

 mechanism explain these phenom- 

 ena, he will not only not be con- 

 tradicted, but will, moreover, have 

 the abundant thanks of the learned 

 world. But in the meantime, to 

 compare gravitation, which is a phe- 

 nomenon or actual matter of fact, 

 with Epicurus' declination of atoms 

 seems to be a very extraordinary 

 method of reasoning" ( 118-124, 

 Leibniz's ' Ph^osophische Schrif- 

 ten,' by Gerhardt, Berlin, 1890, vol. 

 vii. p. 439 sq.) 



1 A very complete account of 



these different attempts will be 

 found in the writings of C. Isen- 

 krahe, ' Das Kiithsel von der 

 Schwerkraft,' Braunschweig, 1879 ; 

 ' ' Euler's Theorie von der Ursache 

 der Gravitation," in ' Zeitschrift fiir 

 Mathematik und Physik,' vol. xxvi. ; 

 ' Ueber die Fernkraft,' Leipzig, 

 1889; " Ueber die Zuriickfiihrung 

 der Schwere auf Absorption," in 

 ' Abhaudlungen zur Geschichte der 

 Mathematik,' vol. vi., Leipzig, Teub- 

 ner, 1892. See also as bearing on 

 this subject, Paul du Bois-Reymond, 

 ' Ueber die Grundlagen der Erkennt- 

 niss in den exacten Wissenschaft- 

 en,' Tiibingen, 1890. 



