- ternatural knowledge. In an age of so much dogmatism,
he first laid down the grand principle of Bacon, that experiment and observation must be the guides to just theory in the investigation of nature." His scientific knowledge proved the means of conferring incalculable benefits upon the art of painting, one of the most important of which was the invention of the chiaro-scuro. His intimate acquaintance with mathematical studies enabled him to develope greatly the knowledge of optics, and no one was better acquainted with the nature of aërial perspective, which became a distinctive and hereditary characteristic of his school. Lanzi says, "Being extremely well versed in poetry and history, it was through him that the Milanese school became one of the most accurate and observing in regard to antiquity and to costume. Mengs has noticed that no artist could surpass Vinci in the grand effect of his chiaro-scuro. He instructed his pupils to make as cautious a use of light as of a gem, not lavishing it too freely, but reserving it always for the best place. And hence we find in his, and in the best of his disciples' paintings, that fine relief, owing to which the pictures, and in particular the countenances, seem as if starting from the canvass."
DA VINCI'S WRITINGS.
Almost of equal value with the pictures of this
immortal artist, are his writings, part of which, un-
