X Preface 



more apt for loquacity and ostentation than for the 

 speculation and discovering of the more abstruse 

 secrets of Nature; which kind of people, before they 

 can be brought to pronounce that wise, ingenious, and 

 modest sentence, I know it not, suffer to escape from 

 their mouths and pens all manner of extravagancies." 

 And he added : ' ' But amongst all the famous men that 

 have philosophated upon this admirable effect of 

 Nature, I wonder more at Kepler than any of the rest, 

 who being of a free and piercing wit, and having the 

 motion ascribed to the Earth before him, hath for all 

 that given ear and assent to the Moon's predominancy 

 over the Water, and to the occult properties, and such 

 like trifles." ^ 



As far as it went Kepler's theory was undoubtedly 

 correct and Galileo's ingenious attribution of the tides 

 to a combination of complex motions of the Earth was 

 incontestably wrong. And certainly Kepler was not 

 to be blamed for the vagueness of his theory considering 

 that it was expressed two centuries before the composi- 

 tion of the Mecanique Celeste, at a time when it was 

 impossible for him to know the theory of gravitation, to 

 become acquainted with the necessary mathematical 

 tools of research, or to command the indispensable 

 tidal observations. 



We who are concerned with economic cycles — the 

 tides in the affairs of men — may learn much from the 

 subsequent history and theory of terrestrial tides. The 

 theory of their cause passed from the stage of a promis- 

 ing speculation to that of a well-ordered working 

 hypothesis when it took the rigid mathematical form 



1 The translation by Thomas Salisbury, 1661, pp. 406-407, 422. 



