While thus employed, the heavy pewter lamp suspended in chains over his head, continually rocked with the motion of the ship, and for ever threw shifting gleams and shadows of lines upon his wrinkled brow, till it almost seemed that while he himself was marking out lines and courses on the wrinkled charts, some invisible pencil was also tracing lines and courses upon the deeply marked chart of his forehead.
But it was not this night in particular that, in the solitude of his cabin, Ahab thus pondered over his charts. Almost every night they were brought out; almost every night some pencil marks were effaced, and others were substituted. For with the charts of all four oceans before him, Ahab was threading a maze of currents and eddies, with a view to the more certain accomplishment of that monomaniac thought of his soul.
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.