xiv PLAN OF THE WORK 
There are infinite variations in the markings of feathers, and those 
figured present only the patterns most frequently met with. The 
Fie. 1. Topography of a bird. (Bluebird, slightly reduced.) 
shaft of the feather is the midrib, to either side of which the vanes, 
or webs, are attached. (See Fig. 2.) 
The Keys.—It is of the utmost importance thoroughly to under- 
