However pleasant, though, the conversation might be, the smallest change in external circumstances, the least break in the perpetual—­

‘Quocumque adspicias, nil est nisi pontus et aer,’

even a passing bird, if one would pass, which none would do save once or twice a stately tropic-bird, wheeling round aloft like an eagle, was hailed as an event in the day; and, on the 9th of December, the appearance of the first fragments of gulf-weed caused quite a little excitement, and set an enthusiastic pair of naturalists—­a midland hunting squire, and a travelled scientific doctor who had been twelve years in the Eastern Archipelago—­fishing eagerly over the bows, with an extemporised grapple of wire, for gulf-weed, a specimen of which they did not catch.  However, more and more still would come in a day or two, perhaps whole acres, even whole leagues, and then (so we hoped, but hoped in vain) we should have our feast of zoophytes, crustacea, and what not.

Meanwhile, it must be remembered that this gulf-weed has not, as some of the uninitiated fancy from its name, anything to do with the Gulf Stream, along the southern edge of which we were steaming.  Thrust away to the south by that great ocean-river, it lies in a vast eddy, or central pool of the Atlantic, between the Gulf Stream and the equatorial current, unmoved save by surface-drifts of wind, as floating weeds collect and range slowly round and round in the still corners of a tumbling-bay or salmon pool.  One glance at a bit of the weed, as it floats past, showed that it is like no Fucus of our shores, or anything we ever saw before.  The difference of look is undefinable in words, but clear enough.  One sees in a moment that the Sargassos, of which there are several species on Tropical shores, are a genus of themselves and by themselves; and a certain awe may, if the beholder be at once scientific and poetical, come over him at the first sight of this famous and unique variety thereof, which has lost ages since the habit of growing on rock or sea-bottom, but propagates itself for ever floating; and feeds among its branches a whole family of fish, crabs, cuttlefish, zoophytes, mollusks, which, like the plant which shelters them, are found nowhere else in the world.  And that awe, springing from ’the scientific use of the imagination,’ would be increased if he recollected the theory—­not altogether impossible—­that this sargasso (and possibly some of the animals which cling to it) marks the site of an Atlantic continent, sunk long ages since; and that, transformed by the necessities of life from a rooting to a floating plant,

‘Still it remembers its august abodes,’

and wanders round and round as if in search of the rocks where it once grew.  We looked eagerly day by day for more and more gulf-weed, hoping that

’Slimy things would crawl with legs
   Upon that slimy sea,’