68 



OUTLINES OF GEOLOGY. 



(3.) In some countries almost every formation which we 

 have classed in the five orders, has been found in the very 

 position assigned to it. The best known instance is in Eng- 

 land, where, if a traveller set out from the mountains of 

 Cumberland, he may pursue such a line in travelling south- 

 eastwards to the British channel, as will carry him over the 

 outcrop of every one of the five orders, and over every indi- 

 vidual formation, except the conchitic limestone of the triasic 

 group. 



These orders, with their groups and series, will be found 

 to occur superinposed in the manner which has been set 

 forth. 



It yet remains to be ascertained, whether some countries, 

 when explored, may not exhibit rocks and formations un- 

 known in those countries where geology has been best 

 studied. 



(4.) Every one of the four first orders abounds in organic 

 remains, and these are found to differ from each other, not 

 only in species and genera, but in families. In some cases, 

 even in formations in immediate contact, this difference is so 

 great as to make it appear as if all the animal life which had 

 existed during the deposit of the lower order, had been de- 

 stroyed, and replaced by a new creation. In proceeding 

 downwards, we find that the mammalia gradually disappear, 

 none except the marsupia reaching as low as the supermedial 

 order, where even that family is extremely rare ; and in the 

 lowest formations, all vertebrated animals, except fish, cease 

 to be found. The latter, of all animals, furnishes the strong- 

 est proof of the succession of the stratified rocks, which has 

 yet been adduced. The researches of Agassiz have shown 

 that the character of fossil fishes does not change by insen- 

 sible degrees from one formation to another, as is frequently 

 the case with molluscous and radiated animals, but is always 

 abrupt. Among all the fossil fish he did not find one which 



