GO SECONDARY SEPaES. 



tinct species, which were swept from the earth ere the for- 

 mation of the transition strata was completed. Our instru- 

 ments of cutlery, the tools of our mechanics, and the count- 

 less machines which we construct, by the infinitely varied 

 applications of iron, are derived from ore, for the most part 

 coeval with, or more ancient than the fuel, by the aid of 

 which we reduce it to its metallic state, and apply it to in- 

 numerable uses in the economy of human life. Thus from 

 the wreck of forests that waved upon the surface of the pri- 

 meval lands, and from ferruginous mud that was lodged at 

 the bottom of the primeval waters, we derive our chief sup- 

 plies of coal and iron ; those two fundamental elements of 

 art and industry, which contribute more than any other 

 mineral production of the earth, to increase the riches and 

 multiply the comforts, and ameliorate the condition of man- 

 kind. 



CHAPTER VIII. 



Strata of the Secondary Series. 



We may consider the history of secondary, and also of 

 tertiary strata, in two points of view: the one, respecting 

 their actual state as dry land, destined to be the habitation 

 <oi man; the other, regarding their prior condition, whilst 

 in progress of formation at the bottom of the waters, and 

 occupied by crowds of organic beings in the enjoyment of 

 life.* 



'^'' The secondary s'ratra are composed of extensive beds of sand and 

 Handstone, mixed occasionally with pebbles, and alternating with deposites 

 of clay, and marl, and limestone. The materials of most of these strata ap- 

 pear to have been derived from the detritus of primary and transition rocks; 

 and the larger fragments, which are preserved in the form of pebbles, 



