46 THEORY OF THE EARTH. 



ignorant of facts, several of whom had even tra- 

 velled extensively for the purpose of examining 

 them, and who, in this manner, made numerous 

 and important additions to science. 



Causes of these differences. 



Whence comes it, then, that there should be 

 so much contrariety in the solutions of the same 

 problem, that are given by men who proceed up- 

 on the same principles ? May not this have been 

 occasioned by the conditions of the problem ne- 

 ver having been all taken into consideration at 

 once ; by which it has remained hitherto indeter- 

 minate, and susceptible of many solutions, all* 

 equally good, when such or such conditions are 

 abstracted ; and all equally bad, when a new con- 

 dition comes to be known, or when the attention 

 is directed to some condition which had been for- 

 merly neglected ? 



Nature and Conditions of the Problem. 



To quit the language of mathematics, it may 

 be asserted, that almost all the authors of these sys- 

 tems, confining their attention to certain difficul- 

 ties which struck them more forcibly than others, 

 have endeavoured to solve these in a manner more 

 or less plausible, and have left unnoticed others, 

 equally numerous, and equally important. For 

 example, the only difficulty with one consisted in 



