240 M. Brongniart on the importance 



this principle by longer discussion, it will be sufficient to 

 cite one fact : The rocks of Calabria have been, during 

 thirty-eight years, the theatre of terrible disturbances ; ho- 

 rizontal beds have been set on their edges, entire masses of 

 rocks have been transported to a distance, and have been 

 placed in unconformable stratifications on other rocks, and 

 no geologist has proposed to consider these masses and rocks 

 as of a different geological epoch. Circumstances of greater 

 value, much more general phenomena, and periods of longer 

 duration, are required for the change of organized bein^rs. 

 The rocks of Calabria suffered, in a short time, derange- 

 ments which may be compared to those observed in the beds 

 of the Alps, but during five or six thousand years organized 

 species have not manifested any appreciable change in their 

 form and other qualities. 



Yet I do not pretend to state that characters derived from 

 the relative disposition of beds (but not the evident super- 

 position) (superposition evidente), their nature, &c. should 

 not be employed, even with confidence, by geologists, to 

 determine different epochs of formation ; alone or united 

 with those derived from the organic remains, they are of 

 the greatest value ; but I consider, and I think that I have 

 good reasons for this opinion, that when these characters are 

 opposed to those drawn from the presence of organic re- 

 mains, the preference should be given to the latter. 



It must be confessed that much attention and caution 

 should be used in the employment of this character. I am 

 not ignorant that the influence of horizontal distances or 

 climates on specific differences should be distinguised and 

 estimated ; that we should learn to appreciate the apparent 

 and sometimes real resemblances that some species present 

 in very different formations, and which have possessed the 

 rare privilege of surviving the destruction of their contem- 

 poraries ; and to continue the same amidst all the changes 

 which have taken place around them : — I am not ignorant 

 that we should also learn to recognise the individuals torn 

 from other rocks, and transported by certain causes into 

 newer rocks, and to distinguish them from those which have 



