Ornithology. 207 



ferent organs situated on the anterior margin of the body of the 

 animal, and composed of the testaceous matter which is excreted 

 by these organs. 



The nature of the process is the same as in univalve shells of a 

 spiral form. The diversity only appears in the difference of the 

 organs, and structure of the animals which inhabit different shells. 

 To a similar process may be ascribed the formation of stris, of 

 scales, and of various excavations which sometimes accompany 

 them. 



ORNITHOLOGY. 



NO. VII. 



Pulverizing of Birds. Among the singularity of manners, 

 perhaps there is none more extraordinary than that which seems 

 peculiar to a few species; by some, called pulverizing, which is 

 that of dusting themselves; it is observable only in the gaUina- 

 ceous tribe; the sky lark, wood lark and house sparrow. These are 

 frequently seen in hot weather to roll themselves in the dust, and 

 by means of their wings and legs, throw it all over their bodies. 

 For what purpose it is intended, is difficult to ascertain. Some 

 have imagined it is to destroy the pediculi with which these birds 

 abound; but as all other birds are troubled with lice, and do not 

 pulverize, the opinion does not seem to be well founded. Oth- 

 ers have supposed that it is to cool themselves, and, that such 

 birds do not wash; but in this also they are mistaken, for no bird 

 bathes more frequently than the sparrow. 



Walk of Birds. All aquatic birds and waders walk or run 

 in the ordinary m.anner, placing one leg before the other alternate- 

 ly ; but a greater portion of the smaller land birds hop or rather 

 jump along, as if their legs were tied together. 



Swimming of Birds. The superior velocity with which 

 aquatic birds swim under water, has not wholly escaped notice; 

 but it is not entirely produced by the action of the wings, which 

 are sometimes used as fins to accelerate the motion, but is occa- 

 sioned by the pressure of the water above. In swimming on the 

 surface, a bird has two motions; one upward, the other forward 

 at every stroke of the feet; so, that when covered with water, 

 that force which was lost by the upward motion, is all directed to 

 tthe progressive, by which it is enabled to pursue its prey, or to 



