460 THE EMPIRE OF THE AIR. 



vincing-, but, alas, it is beyond the reach of most persons. It is not 

 in Paris that tlie seeker will become couviuced, it is not even in Europe, 

 where soaring birds are so rare that months; may pass without one 

 being seen. 



In short, one nuist go abroad to enter tliis new path of investigation ; 

 the path through wliicli I liave reached absolute conviction, and which 

 must be followed by all who desire to know what can be done. If they 

 will thus observe the soaring birds in their own habitat, they will 

 doubtless witness all tlie performances which 1 have flescribed, and 

 probably still others which have escaped me. 



But to be convinced a man must see; for to see, even only once, is 

 better than a whole volume of explanations. Tlierefore, O reader, if 

 you are interested in this subject, go and see for yourself and be 

 edified. Go to the regions where dwell the birds which perform these 

 demonstrations; and when you have beheld them for a few instants, 

 being already initiated as to what to observe, comprehension will at 

 once come into your understanding. 



Imperfeet maehiiies. — It is somewhat unfortunate that I have not suf- 

 ficient space left for a little treatise upon ''paper arrows.'' This school 

 boy's toy, simple as it may seem, is quite instructive when its principles 

 are studied. The arrow may be constructed in various forms, from the 

 acute triangle, which is the type of si)eed, to the broadside rectangle, 

 the aeroplane type, proportioned like a stormy petrel, in which the plane 

 is narrowest m tln^. direction of its motion. 



Moreover, we note that nature has not constructed all sailing birds 

 upon the same model. If we compare the aspect of the great tawny 

 vulture with that of the stormy petrel, who sails wonderfully in a high 

 wind; or with the aspect of the tern, or the gannet, or the frigate-bird, 

 when the latter assume their arrow-like forms, Ave shall licrceive that 

 there is a great diversity of models; we might even say there is an 

 antagonism in models, for we have noted that all of them are perfect 

 in their flight as considered in relation to their life needs. But, not- 

 withstanding these diversities, the gliding flight of each creature, 

 whether supported on elongated or on square wings, is always based 

 upon the same general principle; it results from the possibility of shift- 

 ing the center of gravity by a change in the position of the sustaining 

 surfaces, and this confers the faculty of maintaining equipoise in the air. 

 Ai^roplanes, provided with the necessary sustaining surfaces, and 

 equipped with this faculty, will be sufilicient to reproduce the sailing 

 evolutions of the birds. We may now conclude, therefore, that a par- 

 ticular, special shape is really not indispensable for aerial locomotion; 

 all sorts of forms, even the most curious, may be utilized; only, they 

 will produce the reipiired decompositions of forces, under the action of 

 the wind, in the ratio of their individual perfections. 



Man may succeed in gliding on the wind with circular, triangular, 



