THEORY OF THE EARTH. 173 



have been very improperly named by the natural- 

 ists who have described them ; of the black slate 

 of Glacis ; of the white slate of Aichstedt, also 

 filled with the remains of fishes, of crabs, and of 

 other marine animals different from shells. All these 

 desiderata have as yet received no satisfactory ex- 

 planation in books of geology ; neither has it been 

 as yet explained, why shells should be found almost 

 everywhere, while fish are confined only to a few 

 places. 



It appears to me, that a consecutive history of 

 such singular deposits would be infinitely more va- 

 luable than so many contradictory conjectures re- 

 specting the first origin of the world and other 

 planets, and respecting phenomena which have 

 confessedly no resemblance whatever to those of 

 the present physical state of the world ; such con- 

 jectures finding, in these hypothetical facts, neither 

 materials to build upon, nor any means of verifica- 

 tion whatever. Several of our geologists resemble 

 those historians who take no interest in the history 

 of France, except as to what passed before the time 

 of Julius Caesar. Their imaginations, of course, 

 must supply the place of authentic documents; 

 and accordingly each composes his romance ac- 

 cording to his own fancy. What would become of 

 these historians, if they had not been assisted in 

 their combinations by the knowledge of posterior 

 facts ? But our geologists neglect exactly those 

 posterior geological facts, which might, at least in 



