( S5S ) 



On the Covering of Birds, considered chiefly with reference to 

 the description and distinction of Species, Genera, and Or- 

 ders. By Mr W. M acgillivray, Assistant to the Regius 

 Keeper of the Edinburgh College Museum, and Correspond- 

 ing Member of the Wernerian Natural History Society. 

 Communicated by the Author. 



XJirds, like quadrupeds, are invested with a covering, w^ich 

 is connected with the skin, and lies immediately upon it. This 

 covering is chemically of the same nature with the hair of mam- 

 mifera, and the scales of reptiles and fishes, but it differs essen- 

 tially in respect to its mechanical structure, being much more 

 complex in its constituent parts than the envelope of these class- 

 es of animals. To this general envelope the name of plumage 

 is given. In ordinary language it is more frequently called the 

 feathers. It is peculiar to birds. 



It may be presumed, that the plumage of birds serves to pro- 

 tect them from the injurious agency of external powers, such as 

 cold, heat, rain, hail, &c. and that it operates in retaining the 

 caloric generated in the body, and in developing or fostering 

 electricity. The varieties of structure, magnitude, and propor- 

 tion, and the degrees of connection, which its parts present, to- 

 gether with the diversified hues, and the varied capabilities of 

 absorbing or reflecting light which it possesses, must, in a sys- 

 tem where every thing is the result of design, originate from 

 peculiar specific necessities, and be subservient to the welfare, 

 or even the existence, of the individuals composing this beauti- 

 ful, and, in many respects, highly interesting class of beings. 

 Upon considerations like these it is not my design to enter. 

 Their developement would constitute a task moro than sufficient 

 to confound the pretensions of the wisest ; and I should more 

 admire the mind that had discovered the causes, relations, con- 

 nections, ends and objects of a feather, than that which had 

 measured the magnitudes and distances of the planets^ traced 

 their orbits, and calculated the velocities of their revolutions. 

 The plumage also answers another very important end in the 

 economy of birds, being the medium of their locomotion in the 

 air, — a faculty which gives them so many advantages over qua- 

 drupeds, and which is not possessed, in an equal degree, by any 

 other class of animals. 



