Leonardo da Vinci in his writings, as in everything else, appears as an original genius. He now and then alludes generally to opinions of "philosophers," but he quotes no authority ancient or modern. Nevertheless, a passage on the nature of colours, particularly where he speaks of the colours of the elements, appears to be copied from Leon Battista Alberti,[8] and from the mode in which some of Leonardo's propositions are stated, it has been supposed[9] that he had been accustomed at Florence to the form of the Aristotelian philosophy. At all events, some of the most important of his observations respecting light and colours, have a great analogy with those contained in the treatise in question. The following examples will be sufficient to prove this coincidence; the corresponding passages in Goethe are indicated, as usual, by the numbers of the paragraphs; the references to Leonardo's treatise are given at the bottom of the page. Aristotle. "A vivid and brilliant red appears when the weak rays of the sun are tempered by subdued and shadowy white,"--154. Leonardo "The air which is between the sun and the earth at sun-rise or sun-set, always invests what is beyond it more than any other (higher) portion of the air: this is because it is whiter."[10] A bright object loses its whiteness in proportion to its distance from the eye much more when it is illuminated by the sun, for it partakes of the colour of the sun mingled with the colour (tempered by the mass) of the air interposed between the eye and the brightness.[11] Aristotle. "If light is overspread with much obscurity, a red colour appears; if the light is brilliant and vivid, this red changes to a flame-colour."[12]--150, 160. Leonardo. "This (the effect of transparent colours on various grounds) is evident in smoke, which is blue when seen against black, but when it is opposed to the (light) blue sky, it appears brownish and reddening."[13] Aristotle. "White surfaces as a ground for colours, have the effect of making the pigments[14] appear in greater splendour."--594, 902. Leonardo. "To exhibit colours in their beauty, the whitest ground should be prepared. I speak of colours that are (more or less) transparent."[15] Aristotle. "The air near us appears colourless; but when seen in depth, owing to its thinness it appears blue;[16] for where the light is deficient (beyond it), the air is affected by the darkness and appears blue: in a very accumulated state, however, it appears, as is the case with water, quite white."--155, 158. Leonardo.