1920] on Leonardo da Vinci 127 



beauty of earth's raiment of plants and flowers is merged imper- 

 ceptibly in the mood of the scientist who saw in nature not only 

 form and colour, but above all light, which St. Augustine called " the 

 queen of colours," and uses nature's profusion as a background 

 whereon to study the incidence of light and shade. 



; ' When the sun is in the east," he says, " all the parts of trees 

 which are illuminated by it are of a most brilliant green, and this is 

 due to the fact that the leaves illuminated by the sun within half our 

 hemisphere, namely, the eastern half, are transparent ; while within 

 the western semicircle the verdure has a sombre hue, and the air is 

 damp and heavy, of the colour of dark ashes, so that it is not trans- 

 parent like that in the east, which is refulgent, and the more so as it 

 is more full of moisture." 



Or this, " Of Landscapes " : — 



" The dark colours of the shadows of mountains at a great distance 

 take a more beautiful and purer blue than do those parts which are 

 in light, and from this it follows that when the rock of the mountains 

 is reddish, the parts of it which are in light are fawn-coloured, and 

 the more brightly it is illuminated the more closely will it retain its 

 natural colour." 



His researches in structure are so exact and so scientific in 

 method as to anticipate the results of subsequent enquiry, as, for 

 instance, in the knowledge his writings reveal of phyllotaxis — the 

 law of quincuncial arrangement of the leaves on the stem — promul- 

 gated in 1658 by Sir Thomas Browne in his " Garden of Cyrus." 



In like manner the discovery that the age of a tree may be told 

 from the number of concentric rings visible in a section of its trunk, 

 with which more than a century later the names of Nathaniel Grew 

 and Marcello Malpighi are associated, is contained in a passage in 

 Leonardo's " Treatise on Painting " (Ludvig, 829). He also states 

 in the same passage that these rings vary in thickness according to 

 the greater or less amount of humidity of each year. 



" In an age of so much dogmatism," wrote Hallain, " it was 

 Leonardo who first laid down the grand principle of Bacon, that 

 experiment and observation must be the guides to just theory in the 

 investigation of nature." 



I have attempted here to summarize a few of the results 

 attained in the course of this investigation. The breadth and 

 variety of their scope may serve to recall the remark of Francis I., 

 who is recorded by Benvenuto Cellini to have said " that he did 

 not believe that any other man had come into the world who 

 had attained so great knowledge as Leonardo." The proof of this 

 lies in the thousand pages of his manuscripts. If it does not fully 

 appear in these extracts, I may plead, just as Leonardo does in the 

 concluding words of one of his anatomical manuscripts, " I have not 

 been hindered either by avarice or negligence, but only by want of 

 time." 



[E. McC] 



