"Now, from this peculiar sideway position of the whale's eyes, it is plain that he can never see an object which is exactly ahead, no more than he can one exactly astern. In a word, the position of the whale's eyes corresponds to that of a man's ears; and you may fancy, for yourself, how it would fare with you, did you sideways survey objects through your ears. You would find that you could only command some thirty degrees of vision in advance of the straight side-line of sight; and about thirty more behind you. If your bitterest foe were walking straight towards you, with dagger uplifted in broad day, you would not be able to see him, any more than if he were stealing upon you from behind. In a word, you would have two backs, so to speak; but, at the same time, also, two fronts (side fronts): for what is it that makes the front of a man - what, indeed, but his eyes?
Moreover, while in most other animals that I can now think of, the eyes are so planted as imperceptibly to blend their visual power, so as to produce one picture and not two to their brains; the peculiar position of the whale's eyes, effectually divided as they are by many cubic feet of solid head, which towers between them like a great mountain separating two lakes in valleys; this, of course, must wholly separate the impressions which each independent organ imparts. The whale, therefore, must see one distinct picture on this side, and another distinct picture on that side; while all between must be profound darkness and nothingness to him. Man may, in effect, be said to look out on the world from a sentry-box with two joined sashes for his window. But with the whale, these two sashes are separately inserted, making two distinct windows, but sadly impairing the view. This peculiarity of the whale's eyes is a thing always borne in mind in the fishery; and to be remembered by the reader in some subsequent scenes.
A curious and most puzzling question might be started concerning this visual matter as touching the Leviathan. But I must be content with a hint. So long as man's eyes are open in the light, the act of seeing is involuntary; that is, he cannot help mechanically seeing whatever objects are before him. Nevertheless, any one's experience will teach him, that though he can take in an indiscriminating sweep of things at one glance, it is quite impossible for him, attentively, and completely, to examine any two things - however large and however small - at one and the same instant of time; never mind if they lie side by side and touch each other. But if you now come to separate these two objects, and surround each by a circle of profound darkness; then, in order to see one of them, in such a manner as to bring your mind to bear on it, the other will be utterly excluded from you contemporary consciousness. How is it, then, with the whale? True, both his eyes, in themselves, must simultaneously act; but is his brain so much more comprehensive, combining, and subtle than man's, that he can at the same moment of time attentively examine two distinct prospects, one on one side of him, and the other in exactly the opposite direction? If he can, then it is a marvelous thing in him, as if man were able to simultaneously go through the demonstrations of two distinct problems in Euclid. Nor, strictly investigated, is there any incongruity in this comparison.
It may be idle whim, but it has always seemed to me, that the extraordinary vacillations of movement displayed by some whales when beset by three or four boats; the timidity and liability to queer frights, so common to such whales; I think that all this indirectly proceeds from the helpless perplexity of volition, in which their divided and diametrically opposite powers of vision must involve them.
Is it not curious, that so vast a being as the whale should see through so small an eye, and hear the thunder through an ear which is smaller than a hare's? But if his eyes were broad as the lens of Herschel's great telescope; and his ears capacious as the porches of cathedrals; would that make him any longer of sight, or sharper of hearing? Not at all. - Why then do you try to 'enlarge' your mind? Subtilize it."
excerpted from Moby Dick,
Chapter 74, The Sperm Whale's Head - Contrasted View
by Herman Melville, 1851