REVOLUTIONS. 105 



only marine exuviae. These appearances occur in the se- 

 condary formations of all ages *. 



The statements which have now been given, relative to 

 the changes which have occurred on the earth''s surface, 

 and in the condition of its inhabitants, point out some of 

 the advantages which the student of zoology may derive 

 from an acquaintance with the truths of geognosy, and how 

 necessary it is to cultivate a knowledge of the history of 

 plants and animals, to qualify for conducting geological spe- 

 culations. These views may probably be submitted to the 

 public at a future period in a more enlarged form. 



An acquaintance with the laws which regulate the geo- 

 graphical distribution of animals, is indispensably necessary 

 in our attempts to Naturalise exotic species. The tempera- 

 ture most suited to their health, — the food most congenial 

 to their taste, and best fitted to their digestive organs, — 

 the situation to which their locomotive powers are best adap- 

 ted, — and the foes against which it is most necessary to 

 guard them, are circumstances on which we ought to be- 

 stow the most scrupulous attention, in order to insure suc- 

 cess. There are many animals which can call forth but 

 few counteracting energies, and consequently, cease to thrive, 



* The action of gravity on the mud, and its organic contents, at the 

 period of the deposition of the strata, may have given to the whole an ar- 

 rangement different from that which prevailed at first. This effect of snh. 

 aidence to which I refer, is displayed in every peat-bog. The lower beds 

 are usually formed of sand, or marl. The beds of the latter consist of all 

 the shells which had been formed in the lake before it was filled up. These 

 have subsided to the bottom, and, along with them, the skeletons of deer or 

 oxen which may have perished in the waters. The lighter peat occupies 

 the surface. That the flcetz strata, at their formation, were in a condition 

 to admit of subsidence, is demonstrated by the complanation of those trees 

 and other remains which lie parallel to the surface of the bed, appearance* 

 which are exhibited in every layer of peat. 



