LEONARDO AND MODERN SCIENCE 73 



alone, he wanted to understand as thoroughly as possible the prin- 

 ciples underlying them. He clearly saw that practice and theory 

 are twin sisters who must develop together, that theory without 

 practice is senseless, and practice without theory hopeless. So it 

 was not enough for him to hit upon a contrivance which answered 

 his purpose; he wanted to know the cause of his success, or, as 

 the case may be, of his failure. That is how we find in his papers 

 the earliest systematic researches on such subjects as the stability 

 of structures, the strength of materials, also on friction which he 

 tried in various ways to overcome. That is not all: he seems to 

 have grasped the principle of automaticity — that a machine is so 

 much the more efficient, that it is more continuous and more in- 

 dependent of human attention. He had even conceived, in a 

 special case, a judicious saving of human labor, that is, what we 

 now call "scientific management." 



His greatest achievement in the field of mechanics, however, 

 and one which would be sufficient in itself to prove his extraor- 

 dinary genius, is his exhaustive study of the problem of flying. It 

 is complete, in so far that it would have been impossible to go 

 further at his time, or indeed at any time until the progress of the 

 automobile industry had developed a suitable motor. These inves- 

 tigations which occupied Leonardo throughout his life, were of 

 two kinds. First, a study of the natural flying of birds and bats, 

 and of the structure and function of their wings. He most clearly 

 saw that the bird obtains from the air the recoil and the resistance 

 which is necessary to elevate and carry itself forward. He ob- 

 served how birds took advantage of the wind and how they used 

 their wings, tails, and heads as propellers, balancers and rudders. 

 In the second place, a mechanical study of various kinds of arti- 

 ficial wings, and of diverse apparatus by means of which a man 

 might move them, using for instance the potential energy of 

 springs, and others which he would employ to equilibrate his ma- 

 chine and steer its course. 



It is necessary to insist that most of these drawings and notes of 

 Leonardo's are not idle schemes, vague and easy sugaesffonsV 7 



