ON THE VAEIOUS MODES OF FLIGHT IN RELATION TO AERONAUTICS. 



By Dr. James Bell Pettigrew. 



[FROM THE PROCEEDINGS OF THK ROYAL INSTITUTION OF GREAT BRITAIN.] 



The subject of fliglit, natural and artificial, is one wLicli lias occupied the 

 attention of mankind from a very early period. 



It involves a more or less intimate acquaintance with anatomy, physiology, 

 mechanics, and the higher branches of mathematics. 



If regarded as a natural movement, it forms one of the three kinds of loco- 

 motion by which animals progress — the remaining two being walking and swim- 

 ming ; if regarded as ani artificial one, it represents the unsolved problem of that 

 grand trio which has for its integral parts the locomotive, steamboat, and Hying 

 machine. Had time permitted, it was my intention to have gone into the subject 

 of locomotion at length. I find, however, I must curtail my remarks imder this 

 head, which I do with reluctance, from a. feeling that the chain of animal move- 

 ments, like the great chain of existence, winds in and out and doubles upon itself 

 so completely as to render a partial examination of it in many respects unsatis- 

 factory. 



The movements of animals are adapted either to the earth, the water, or the 

 air. There are others, however, of a mixed character, where they are suited 

 equally to the land and water, or even to the land, water, and air. 



The instruments by which locomotion is attained are therefore specially 

 modified. 



This is necessary because of the difierent densities and the diflferent degrees 

 of resistance furnished by the land, water, and air respectively. 



As the earth afibrds a greater amount of support than the water, and the water 

 than the air, it requires a greater degree of muscular fexertion to swim than to 

 walk, and a still greater one to fly. 



For this reason flight is the most laborious, and in some respects the most 

 complicated and diflicult, of all the animal movements. 



The })eculiarities of the different media, as far as locomotion is concerned, may 

 be l)riefly stated. 



On the land wo have the maximum of resistance and the minimum of dis- 

 placement. 



In the air, the minimum of resistance and the maximum of displacement. 



The water is intermediate in these respects. 



As a consequence, the feet of land animals are small — their bodies large. 

 The horse and deer furnish examples. 



In those land animals which take to the water occasionally, or the reverse, 

 the feet are enlarged and usually provided with a membranous expansion 

 between the toes. Of such, the otter, ornithorhynchus, seal, irog, turtle and 

 crocodile may be cited. 



In addition to the land animals which run and swim, there are some which 

 precipitate themselves, parachute fashion, from immense heights, and othera 

 which even fly. In these the membranous expansions are greatly increased — 



