!Sq ? I Recant Literature . ^^Q 



the structural' colors, and -subjective structural,' prismatic, or metallic 

 colors. Respecting the distribution of coloring matter he says : "To judge 

 from the growth of a feather, the production of crossbars seems to be the 

 older stage, since they will result from the intermittent deposition of pig- 

 ment, while, on the other hand, the production of shaft-streaks is not vet 

 satisfactorily explained. At any rate, it must be borne in mind that 

 possibly various groups of birds have gone independently through such 

 stages, and that what is primitive or archaic in one need not be so in all." 

 It seems strange not to find under Dimorphism some reference to the 

 familiar phenomenon of dichromatism as exemplified in numerous genera 

 of Owls, Hawks, Goatsuckers, Herons, etc., some of which seemingly 

 should have come to his mind in this connection rather than the far- 

 fetched cases he does cite. In fact, it would seem only fair to expect that 

 a subject of so much importance and interest as dichromatism would at 

 least receive mention, if not be made even the subject of a short article. 



Among other subjects treated at considerable length are Eggs, by New- 

 ton, forming an article of 10 pages; Embryology, by Gadow, iS pages; 

 Extermination, by Newton, 12 pages; Feathers, by Gadow, 10 pages; 

 Flight, by Prof. Roy, 12 pages; Fossil Birds, by Lydekker, S pages. 

 These are all articles of the highest interest and importance, though that 

 on Flight is somewhat disappointing, both in method of treatment and 

 results. For instance, the relation of flight to the form of the wing is 

 given much less consideration than its importance merits; and there is a 

 tendency to treat the subject, and particularly soaring, from the standpoint 

 of the physicist and the mathematician. The fact seems to be ignored 

 that a bird is not a dead weight — a piece of card board, or a lump of dead 

 matter — but a living, sensitive, highly endowed animal. — a living kite, to 

 employ a simile, in which the attraction of gravitation represents the kite- 

 string, while the soaring bird, representing the kite as a whole, under the 

 direction of its keen senses, is constantly, automatically perhaps or at 



least almost unconsciously, trimming its sails — its wings and tail to 



secure its desired course or position. Any one who has observed birds soar- 

 ing under a variety of circumstances need not be told that while "upward 

 currents of air" and "varying velocity of wind at different altitudes " may 

 be necessary for soaring in the opinion of the physicist, birds themselves 

 are not thus restricted, at least to any essential degree. A certain amount 

 of momentum must evidently be acquired, after which birds seem able to 

 soar at pleasure in either a practically calm atmosphere or in a gale of 

 wind ; within a few yards of the surface of the earth or at altitudes almost 

 beyond the reach of the vision. A slight, even almost imperceptible 

 movement of a wing or inclination of the tail may suffice to place the 

 bird in the proper plane to receive a new impetus or enable it to radically 

 change the direction of flight. 



Much of the 'Dictionary,' as already explained, is matter republished 

 with little change from the 'Encyclopaedia Britannica,' but there is a great 

 deal that has been expressly written for the present work. The illustra- 



