104 Ornithology. 



Pearl. The constituent parts of pearl appear to be simi- 

 lar to those of mother of pearl. They are composed of con- 

 centric coats of membrane and carbonate of lime, and resem- 

 ble, in structure, the globular, calcareous concretions, which 

 are known by the name of pisolithes. The iridescence and 

 undulated appearance of pearl and mother of pearl, evidently 

 depend on their lamellated structure and semi-transparency. 

 From these experiments, it appears that shells are composed 

 of carbonate of lime and gluten. In some, as in the porcella- 

 neous shells, the proportion of carbonate of lime is great, 

 while that of the animal matter is small ; and these may be 

 regarded as the beginning of the series, while shells that 

 come under the description of mother of pearl are to be 

 placed at the oiher extremity, having a smaller proportion of 

 carbonate of lime, and a greater proportion of membrana- 

 ceous substance. In the first, the carbonate of lime is nearly 

 cemented by the animal matter ; in the latter, the carbonate 

 of lime serves to harden the membranaceous substance. But 

 between these two extremes, in the proportion of carbonate 

 of lime and animal gluten, of which all testaceous substan- 

 ces are composed, there are, no doubt, numerous intermedi- 

 ate gradations, arising from the nature of the animal to which 

 they form a covering, its peculiar habits, or mode of life. 



ORNITHOLOGY. 



NO. IV. 



Song of birds. As the song of birds is not allowed to be 

 the effect of love, by an honorable author on the subject of 

 singing birds,* we shall endeavor to elucidate this matter 

 from experiments on birds, in their natural wild state ; and 

 also endeavor to prove that their notes are innate, contrary to 

 that author's opinion. That confined birds will learn the 

 song of others they are constantly kept with, there is no doubt ; 

 but then it is generally blended with that peculiar to the 

 species. In the spring, the very great exertions of the male 

 birds in their vociferous notes are certainly the calls to love ; 

 and the peculiar note of each is an unerring mark for each to 

 discover its own species. If a confined bird had learned the 

 song of another, without retaining any part of its natural 



* Daines Barrington. 



