PREFACE. XV 



labour ; and the doubts which thence arose respecting 

 their truth, were of a nature to demand frequent 

 comparisons, and repeated examinations. 



Such as the facts are, I have however attempted, 

 as far as the plan of the work permitted, to place 

 them in such a light as to render them useful to 

 those who may possess greater inclination or greater 

 power to arrange them under some general theory. 

 If they feel the same difficulties in this respect as 

 myself, they will not be in haste. Wherever the 

 observations disagree with received opinions, I can 

 only trust that the references to the places where 

 they were made, are so precisely detailed that any 

 one may find the means either of verifying or of 

 correcting them. If there are inconsistencies, it is 

 to be hoped that they will be found to lie between 

 the facts and previous opinions : they may often, 

 perhaps, exist in the observations ; but they will 

 not be found in Nature. To investigate well is 

 the first duty of a naturalistj and to relate the truth 

 is the duty of all; but every one imagines himself 

 alone to be free of prejudices. There is much yet 

 to be done by those who cultivate this science, but 

 in pursuing his investigations, it is especially necessary 

 for the geologist never to lose sight of the rule of 

 Seneca ; 



" Nihil magis praestandum quam ne pecorum ritu sequamur 

 antccedentium gregem, pergentes non qud cundem cst sed qua 

 itur." 



