8 PREFACE. 



distribution, and the various relations of the objects to 

 which it refers. No person qualified to construct a 

 satisfactory system of arrangement has yet appeared ; 

 nor is the requisite knowledge possessed by our race 

 collectively, much less by any individual. Artificial or 

 temporary methods of arrangement, therefore, are the 

 only kinds that can be employed ; and the so-called 

 " natural systems," whether in Zoology or in Botany, 

 are as artificial as those confessedly such. They ought 

 to be named Relational or Analogical Systems. 



The species of birds may be disposed with reference 

 to their afl&nities in various orders or series, according 

 as the consideration of one or other organ is assumed 

 as the basis of arrangement. But as the organs of an 

 individual in the series do not undergo equal or analo- 

 gous modifications, the idea of linear series as capable 

 of connecting species by general affinity must be aban- 

 doned. In one point of organization, a species may be 

 allied to another, while in a second point it may resem- 

 ble a third species ; in one point it may adhere to ano- 

 ther shewing an evident general similarity, while in 

 another it may indicate an intimate relation to a species 

 which yet in other respects differs extremely. 



The collocation of several species constitutes a sub- 

 genus, a genus, or a family. But as there are few 

 abrupt boundaries among birds, divisions are often mere- 

 ly arbitrary ; whence it happens that what one calls a 

 class, another considers as an order, or even a genus. 



