THEORY OF THE EARTH, 105 



tive organs in those species- which have less per- 

 fect masticatory systems ; and hence we may pre- 

 sume that these latter animals require especially 

 to be ruminant, which are in want of such or such 

 kinds of teeth; and may also deduce, from the 

 same considerations, the necessity of a certain 

 conformation of the esophagus, and of correspond- 

 ing forms in the vertebrae of the neck, &c. But 1 

 doubt whether it would have been discovered, in- 

 dependently of actual observation, that ruminant 

 animals should all have cloven hoofs, and that they 

 should be the only animals having that particular 

 conformation; that the ruminant animals only 

 should be provided with horns on their foreheads ; 

 that those among them which have sharp tusks, or 

 canine teeth, should want horns, &c. 



As all these relative conformations are constant 

 and regular, we may be assured that they depend 

 upon some sufficient cause; and, since we are not 

 acquainted with that cause, we must here supply 

 the defect of theory by observation* and in this 

 way lay down empirical rules on the subject, which 

 are almost as certain as those deduced from ra- 

 tional principles, especially if established upon 

 careful and repeated observation. Hence, any 

 one who observes merely the print of a cloven 

 hoof, may conclude that it has been left by a rumi- 

 nant animal, and regard the conclusion as equally 

 certain with any other in physics or in morals. 

 Consequently, this single foot-mark clearly ijidi- 



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