1920] on Leonardo da Vinci 121 



From the meagre records of the attempt we pass to the researches 

 in theory and construction. In an article in the " Nineteenth 

 Century " ten years ago I attempted a fuller analysis of these than 

 is here possible, and I may be permitted to quote a sentence from 

 my article : — 



" The material falls naturally into two groups, the first being a 

 series of investigations of the laws which govern the power of flight 

 as manifested in nature by birds and other winged creatures, the 

 second consisting of deductions from these principles in the construc- 

 tion of a mechanism which should be capable of sustaining and being 

 worked by man. The inter-dependence of the two parts of the 

 enquiry is stated with great succinctness in a passage in the Codice 

 Atlantico : — 



" ' A bird is an instrument working according to mathematical 

 law, which instrument it is within the capacity of man to reproduce 

 with all its movements, but not with a corresponding degree of 

 strength, though it is deficient only in the power of maintaining 

 equilibrium. We may therefore say that such an instrument con- 

 structed by man is lacking in nothing except the life of the bird, 

 and this life must needs be supplied from that of man. 



" ' The life which resides in the bird's members will without doubt 

 better conform to their needs than will that of man which is separated 

 from them, and especially in the almost imperceptible movements 

 which preserve equilibrium. 



" ' But since we see that the bird is equipped for many obvious 

 varieties of movements, we are able from this experience to deduce 

 that the most rudimentary of these movements will be capable of 

 being comprehended by man's understanding ; and that he will to a 

 great extent be able to provide against the destruction of that 

 instrument of which he has himself become the living principle and 

 the propeller.' " 



In the analogy thus drawn from nature to the problem before 

 him Leonardo has anticipated the attitude of modern research. 



In his construction of the instrument he finally attempted to 

 combine the type of the lark soaring with its wings open with that 

 of the bat as it descends. He does this by the introduction of 

 sportelli (trap-doors or shutters) in the surface of the wings, whereby, 

 as he says, " the wing is full of holes as it rises and closes up when 

 it falls." The shutters should have rims of cane and be covered 

 with starched taffeta to render them airtight. Perhaps it was after 

 the Monte Ceceri attempt that he wrote on a page of MS. B of the 

 Paris MSS., "Try the actual instrument in the water, so that if you 

 fall you will not do yourself any harm." It may also have been the 

 failure of this attempt that caused him to search for a fresh source 

 of motive power to take the place of that exerted by the muscles of 

 a man. On 83 verso, MS. B of the Paris MSS., there is a drawing 

 of a large screw constructed to revolve round a vertical axis, and a 

 note explains its intended use : " If this instrument made with a screw 



