Even between the tropics, the phosphoric light is increased or diminished in its degree of brilliancy, in a very slight difference of latitude; on one day it would be seen to a most magnificent extent, on the next it would be perhaps merely a few luminous flashes. It might proceed from the shoals of marine animals, that caused the brilliancy to be less extensively distributed over one part of the ocean than another. That I am correct in asserting that some of the animals which occasion the phosphoric light, emitted by the ocean, do travel in shoals, and are distributed in some latitudes only in a very limited range, I insert two facts which occurred during this voyage, and which will no doubt be regarded as interesting.
On the 8th of June, being then in latitude 00° 30′ south, and longitude 27° 5′ west, having fine weather and a fresh south-easterly trade wind, and range of the thermometer being from 78° to 84°, late at night the mate of the watch came and called me to witness a very unusual appearance in the water, which he, on first seeing, considered to be breakers. On arriving upon the deck, this was found to be a very broad and extensive sheet of phosphorescence, extending in a direction from east to west as far as the eye could reach; the luminosity was confined to the range of animals in this shoal, for there was no similar light in any other direction. I immediately cast the towing net over the stern of the ship as we approached nearer the luminous streak, to ascertain the cause of this extraordinary and so limited a phenomenon. The ship soon cleaved through the brilliant mass, from which, by the disturbance, strong flashes of light were emitted; and the shoal (judging from the time the vessel took in passing through the mass) may have been a mile in breadth: the passage of the vessel through them, increased the light around to a far stronger degree, illuminating the ship. On taking in the towing net, it was found half filled with pyrosoma, (atlanticum?) which shone with a beautiful pale greenish light, and there was also a few small fish in the net at the same time; after the mass had been passed through, the light was still seen astern until it became invisible in the distance, and the whole of the ocean then became hidden in darkness as before this took place. The scene was as novel as it was beautiful and interesting, more so from having ascertained, by capturing the luminous animals, the cause of the phenomenon.
The second was not exactly similar to the preceding; but, although also limited, was curious, as occurring in a high latitude during the winter season. It was on the 19th of August,[15] the weather dark and gloomy, with light breezes from north-north-east, in latitude 40° 30′ south, and longitude 138° 3′ east, being then distant about three hundred and sixty-eight miles from King’s Island, (at the western entrance of Bass’s Straits). It was about eight o’clock, P.M. when the ship’s wake was perceived to be luminous, and scintillations of the same light were also abundant around. As this was unusual and had not been seen before, and it occasionally also appeared in larger or smaller detached masses giving out a high degree of brilliancy: to ascertain the cause, so unusual in high latitudes during the winter season, I threw the towing net overboard, and in twenty minutes succeeded in capturing several pyrosoma, giving out their usual pale green light; and it was no doubt detached groups of these animals, that were the occasion of the light in question. The beautiful light given out by these molluscous animals soon subsided, (being seen emitted from every part of their bodies,) but by moving them about it could be reproduced for some length of time after. As long as the luminosity of the ocean was visible, (which continued most part of the night,) a number of Pyrosoma atlanticum, two species of Phyllosoma, an animal apparently allied to Leptocephalus, as well as several crustaceous animals, all of which I had before considered as inter-tropical species, were caught and preserved. At half-past ten, P.M. the temperature of the atmosphere on deck was 52°, and that of the water 51½°. The luminosity of the water gradually decreased during the night, and towards morning was no longer seen, nor on any subsequent night.[16]
Albicores,[17] bonitos, and even a colossal whale close under the stern, beguiled a tedious hour, until we arrived in latitudes where the various species of albatross, cape petrel, and other oceanic birds afforded a change from the “finny” to the “feathered” tribe. We lost the south-east trade on the 13th of June, in about 14° 30′ south, and long. 32° 14′. west. In lat. 30° 0′ south, and long. 24° 18′ west, on the 25th of June, cape petrels[18] were first seen, and increased in numbers as we proceeded, continuing about the ship, in greater or less numbers, even to Port Jackson; albatrosses were not seen until we arrived in lat. 36° south, long. 5° 18′ west, when several species of this bird were often about the vessel.
Besides the sight of flying fish, sharks, dolphins, and other deep-water fish; cape petrels, albatrosses, and other oceanic birds, serve to banish the sameness of a sea voyage, and that ennui which lays its benumbing hand upon those who have but few resources in themselves, and looking for it in objects around, too often feel disappointed. It is usually about the 29° of latitude, and 26° of west longitude, that the gigantic species of albatross is usually first seen, as well as the smaller but not less elegant species of the same bird. At first but few are seen, but they increase in numbers as the vessel gets into more southern latitudes; at some seasons of the year they appear more numerous than at others, which may be attributed to the pairing time, which may keep them, at certain seasons, nearer the rocky islets upon which they breed or rear their young. The large white or wandering albatross,[19] (Diomedia exulans,) the type of the genus, excites much interest by its majestic appearance, either when almost sweeping the sides of the vessel with its huge pinions, or when beheld a prisoner on the ship’s deck, realizing the idea of the famed roc (allowing for the brilliant and exaggerated descriptions usual in all eastern nations) mentioned in the Arabian Nights’ Entertainments.[20]
It is pleasing to observe this superb bird sailing in the air in graceful and elegant movements, seemingly excited by some invisible power, for there is rarely any movement of the wings seen, after the first and frequent impulses given, when the creature elevates itself in the air; rising and falling as if some concealed power guided its various motions, without any muscular exertion of its own; and then descending sweeps the air close to the stern of the ship, with an independence of manner, as if it were “monarch of all it surveyed.” It is from the very little muscular exertion used by these birds, that they are capable of sustaining such long nights without repose.
When these elegant birds are captured, and brought on board, their sleek, delicate and clean plumage is a subject of much admiration; and the fine snow-white down which remains after the removal of the outer feathers, is in requisition among ladies for muffs, tippets, &c. The large species of albatross measures from eight to fourteen feet. I have even heard it asserted, that specimens have been shot of this species, the expanded wings of which measured twenty feet across; but the greatest spread I have seen, has been fourteen feet.[21] The immense distance these birds are capable of flying, seems almost incredible, although often ascertained by birds having been caught, marked, and again set at liberty. When seizing an object floating on the water, they gradually descend with expanded or upraised wings, or sometimes alight, and float like a duck on the water, while devouring their food; then, elevating themselves, they skim the surface of the ocean with expanded wings, giving frequent impulses, (as the great length of their wings prevents their rising with facility from a level surface,) as they run along for some distance, until they again soar in mid-air, and recommence their erratic flights. It is interesting to view them during boisterous weather, flying with, and even against, the wind, seeming the “gayest of the gay” in the midst of howling winds and foaming waves.
To watch the flight of these birds used to afford me much amusement;—commencing with the difficulty experienced by them in elevating themselves from the water. To effect this object, they spread their long pinions to the utmost, giving them repeated impulses as they run along the surface of the water for some distance. Having, by these exertions, raised themselves above the wave, they ascend and descend, and cleave the atmosphere in various directions, without any apparent muscular exertion. How then, it may be asked, do these birds execute such movements? The whole surface of the body in this, as well as, I believe, most, if not all, the oceanic tribes, is covered by numerous air-cells, capable of a voluntary inflation or diminution, by means of a beautiful muscular apparatus. By this power, the birds can raise or depress themselves at will, and the tail, and great length of the wing, enable them to steer in any direction. Indeed, without some provision of this kind, to save muscular exertion, it would be impossible for these birds to undergo such long flights without repose, as they have been known to do; for the muscles appertaining to the organs of flight, although large in these birds, are evidently inadequate in power to the long distances they have been known to fly, and the immense length of time they remain on the wing, without scarcely a moment’s cessation.
When several species of the albatross, as well as petrels and other oceanic birds, are about the ship at the same time, no combats have been seen to take place between them; but on the death of one, the others soon fall upon and devour it. When one of this tribe of birds is captured and brought upon the deck, it appears to be a very muscular bird,—judging from its external form. This deception is occasioned by the quantity of down and feathers, with a very dense integument, and the air-cells being often inflated in a slight degree. When these are removed, the body of the bird is found to be of a smaller size than would have been supposed, and, comparatively speaking, does not possess the muscular power, which, from its long flights, our ideas might lead us to suppose. I remarked that the albatross would lower himself even to the water’s edge, and elevate himself again without any apparent impulse; nor could I observe any percussion of the wings when the flight was directed against the wind,—but then, of course, its progress was tardy. Many, however, have differed with me in considering that the birds never fly “dead against the wind,” but in that manner, which sailors term, “close to the wind,” and thus make progress, aided by, when seemingly flying against, the wind.[22]