548 HISTORY OF GEOLOGY. 



information they conveyed, should be accompanied 

 by geological Sections, or imaginary representations 

 of the order and mode of superpositions, as well as 

 of the superficial extent of the strata, as in more 

 recent times has usually been done. The strata, 

 as we travel from the higher to the lower, come 

 from under each other into view; and this out- 

 cropping, basseting, or by whatever other term it 

 is described, is an important feature in their de- 

 scription. 



It was further noticed that these relations of 

 position were combined with other important facts, 

 which irresistibly suggested the notion of a rela- 

 tion in time. This, indeed, was implied in all theo- 

 ries of the earth; but observations of the facts 

 most require our notice. Steno is asserted by Hum- 

 bolt to be the first who (in 1669) distinguished 

 between rocks anterior to the existence of plants 

 and animals upon the globe, containing therefore 

 no organic remains; and rocks superimposed on 

 these, and full of such remains, "turbidi maris sedi- 

 menta sibi invicem imposita." 



Rouelle is stated, by his pupil Desmarest, to have 

 made some additional and important observations. 

 " He saw," it is said, " that the shells which occur 

 in rocks were not the same in all countries; that 

 certain species occur together, while others do not 

 occur in the same beds ; that there is a constant 



' Essai Geognosfiqne. 



