125. Perhaps you would not call that 'science' at all. It is no matter what either you or I call it. It _is_ science of a certain order of facts. Two summers ago, looking from Verona at sunset, I saw the mountains beyond the Lago di Garda of a strange blue, vivid and rich like the bloom of a damson. I never saw a mountain-blue of that particular quality before or since. My science as an artist consists in my knowing that sort of blue from every other sort, and in my perfect recollection that this particular blue had such and such a green associated with it in the near fields. I have nothing whatever to do with the atmospheric causes of the colour: that knowledge would merely occupy my brains wastefully, and warp my artistic attention and energy from their point. Or to take a simpler instance yet: Turner, in his early life, was sometimes good-natured, and would show people what he was about. He was one day making a drawing of Plymouth harbour, with some ships at the distance of a mile or two, seen against the light. Having shown this drawing to a naval officer, the naval officer observed with surprise, and objected with very justifiable indignation, that the ships of the line had no port-holes. "No," said Turner, "certainly not. If you will walk up to Mount Edgecumbe, and look at the ships against the sunset, you will find you can't see the port-holes." "Well, but," said the naval officer, still indignant, "you know the port-holes are there." "Yes," said Turner, "I know that well enough; but my business is to draw what I see, and not what I know is there." 126. Now, that is the law of all fine artistic work whatsoever; and, more than that, it is, on the whole, perilous to you, and undesirable, that you _should_ know what is there. If, indeed, you have so perfectly disciplined your sight that it cannot be influenced by prejudice;--if you are sure that none of your knowledge of what is there will be allowed to assert itself; and that you can reflect the ship as simply as the sea beneath it does, though you may know it with the intelligence of a sailor,--then, indeed, you may allow yourself the pleasure, and what will sometimes be the safeguard from error, of learning what ships or stars, or mountains, are in reality; but the ordinary powers of human perception are almost certain to be disturbed by the knowledge of the real nature of what they draw: and, until you are quite fearless of your faithfulness to the appearances of things, the less you know of their reality the better.