Melville spiega così la strategia di Achab per scovare Moby Dick negli oceani sterminati (Moby Dick, cap. 44):
Now, to any one not fully acquainted with the ways of the leviathans, it might seem an absurdly hopeless task thus to seek out one solitary creature in the unhooped oceans of this planet. But not so did it seem to Ahab, who knew the sets of all tides and currents; and thereby calculating the driftings of the sperm whale’s food; and, also calling to mind the regular, ascertained seasons for hunting him in particular latitudes; could arrive at reasonable surmises, almost approaching to certainties, concerning the timeliest day to be upon this or that ground in search of his prey.
So assured, indeed, is the fact concerning the periodicalness of the sperm whale’s resorting to given waters, that many hunters believe that, could he be closely observed and studied throughout the world; were the logs for one voyage of the entire whale fleet carefully collated, then the migrations of the sperm whale would be found to correspond in invariability to those of the herring-shoals or the flights of swallows. On this hint, attempts have been made to construct elaborate migratory charts of the sperm whale. […]
Besides, when making a passage from one feeding-ground to another, the sperm whales, guided by some infallible instinct- say, rather, secret intelligence from the Deity- mostly swim in veins, as they are called; continuing their way along a given ocean-line with such undeviating exactitude, that no ship ever sailed her course, by any chart, with one tithe of such marvellous precision. Though, in these cases, the direction taken by any one whale be straight as a surveyor’s parallel, and though the line of advance be strictly confined to its own unavoidable, straight wake, yet the arbitrary vein in which at these times he is said to swim, generally embraces some few miles in width (more or less, as the vein is presumed to expand or contract); but never exceeds the visual sweep from the whale-ship’s mast-heads, when circumspectly gliding along this magic zone. The sum is, that at particular seasons within that breadth and along that path, migrating whales may with great confidence be looked for.
And hence not only at substantiated times, upon well known separate feeding-grounds, could Ahab hope to encounter his prey; but in crossing the widest expanses of water between those grounds he could, by his art, so place and time himself on his way, as even then not to be wholly without prospect of a meeting. [il corsivo è mio]
Insomma, per catturare la tua preda, devi metterti nei suoi panni, pensare come lei, muoverti come lei… In questo Achab, chino sulle carte nautiche nella sua cabina, è probabilmente molto vicino al suo antenato che, schizzando il profilo di un bisonte sulle pareti di una grotta, strologava sul modo migliore di prenderlo…