The movement of the fifteenth century was twofold; partly the Renaissance, partly also the coming of what is called the "modern spirit," with its realism, its appeal to experience. It comprehended a return to antiquity, and a return to nature. Raphael represents the return to antiquity, and Leonardo the return to nature. In this return to nature, he was seeking to satisfy a boundless curiosity by her perpetual surprises, [110] a microscopic sense of finish by her finesse, or delicacy of operation, that subtilitas naturae which Bacon notices. So we find him often in intimate relations with men of science,--with Fra Luca Paccioli the mathematician, and the anatomist Marc Antonio della Torre. His observations and experiments fill thirteen volumes of manuscript; and those who can judge describe him as anticipating long before, by rapid intuition, the later ideas of science. He explained the obscure light of the unilluminated part of the moon, knew that the sea had once covered the mountains which contain shells, and of the gathering of the equatorial waters above the polar. He who thus penetrated into the most secret parts of nature preferred always the more to the less remote, what, seeming exceptional, was an instance of law more refined, the construction about things of a peculiar atmosphere and mixed lights. He paints flowers with such curious felicity that different writers have attributed to him a fondness for particular flowers, as Clement the cyclamen, and Rio the jasmin; while, at Venice, there is a stray leaf from his portfolio dotted all over with studies of violets and the wild rose. In him first appears the taste for what is bizarre or recherché in landscape; hollow places full of the green shadow of bituminous rocks, ridged reefs of trap-rock which cut the water into quaint sheets of light,--their exact antitype is in our own western seas; all the [111] solemn effects of moving water. You may follow it springing from its distant source among the rocks on the heath of the Madonna of the Balances, passing, as a little fall, into the treacherous calm of the Madonna of the Lake, as a goodly river next, below the cliffs of the Madonna of the Rocks, washing the white walls of its distant villages, stealing out in a network of divided streams in La Gioconda to the seashore of the Saint Anne--that delicate place, where the wind passes like the hand of some fine etcher over the surface, and the untorn shells are lying thick upon the sand, and the tops of the rocks, to which the waves never rise, are green with grass, grown fine as hair. It is the landscape, not of dreams or of fancy, but of places far withdrawn, and hours selected from a thousand with a miracle of finesse. Through Leonardo's strange veil of sight things reach him so; in no ordinary night or day, but as in faint light of eclipse, or in some brief interval of falling rain at daybreak, or through deep water.