The winds, then, shifted with much regularity, and with them the atmospheric pressure, just as in the case of cyclones, except that neither the wind nor the sea ever presented the characteristics of a tempest. The wind, which began to blow from the North-East, drew gradually to North, thence West and South, and returned to S.E., after short intervals of calm. We could thus perceive, on referring to the ship's log, that the entire cycle was completed in five or six days; so that it became quite possible, by examining the central direction of the daily variation, to foretell the wind which must be blowing twelve hours later, when, upon taking into consideration the path described by such central direction from day to day, it appeared that the wind described very nearly a parabolic curve.
Even the aspect of the heavens, and the state of the weather, were only one degree less regular in their alternations than the hurricanes. With the S.E. wind, the sky was bright, but as soon as it began to veer round, towards afternoon, a few white belts of cirrhous clouds began to appear in the western heavens, constituting a well-marked division of the vault of the sky from one side quite to the other. As it drew still further round, and neared the line of centres, the weather grew foul, a driving scud covered the heavens, and a succession of splendid rainbows were seen, till the ship had reached the nearest spot to the storm-centre when there were sharp squalls of wind, accompanied by heavy showers of rain. The lower strata of clouds, mere vapour, drove before the wind, while those above moved in a directly contrary direction, generally that of the forthcoming wind. The atmospheric pressure, which at first would be considerable, gradually decreased as we approached the central line; as we drew away from that centre the barometer rose again, the weather improved, and the sky under the influence of southerly winds once more cleared.
Unfortunately it is not practicable with a single ship to ascertain whether the veering of the wind follows an exact curve, as we can only say what is the direction at the spot where the observation has been made, and it is impossible to determine what it may be at other points. But it is at all events certain that the shifts of wind are amenable to the same general laws as hurricanes. A number of ships sent out for the special purpose of this branch of investigation, could render immense services to science and navigation, and achieve most interesting results.
We availed ourselves of these general laws to traverse the ocean as speedily as possible, in order to reach early our next anchorage, and in so doing we experienced altogether three well-marked cycles of wind at short intervals. We cannot afford space to prosecute all the interesting consequences that result from these phenomena of nature, such investigations being more properly reserved for the meteorological section of the scientific portion of this work. Here, however, the facilities for observation of a sea-faring life have been directed towards an object of inquiry, which must prove of immense utility in navigation and commerce. And, perhaps, even landsmen may not find it uninteresting, that even that proverbially fickle element, air, obeys certain fixed laws, a more accurate acquaintance with which must be of the utmost importance to the denizen of terra firma, as well as those "that go down to the sea in ships, that do business in great waters."
On this passage from the American to the African coasts, we were continually accompanied by our winged friends, the sea-birds, which, notwithstanding the unkind treatment they received at the hands of the zoological sportsmen, followed us with the utmost pertinacity, probably attracted by the numerous fragments of provisions thrown overboard.
The Cape pigeons (Procellaria sp.), those prettily-marked sea-birds, about the size of doves, the albatrosses, (Diomedea sp.) the largest of the ocean feathered tribe, with their quiet majestic flight, stormy petrels of all sorts and sizes, from the smallest swallow to the largest of its kind; all these winged inhabitants of the sea's surface followed the frigate in motley groups, and seemed never to weary in their active search for food.
Sometimes they alighted, rested on the surface of the water, and were left far behind; but they collected again with great rapidity as soon as anything eatable appeared, and overtook the frigate in a swift flight from the remotest point of the horizon. This singular attachment to ships very probably arises from their being accustomed to follow whalers, from which such a large quantity of garbage is thrown overboard, very much affected by these aërial parasites, whence they learn to expect from all vessels their favourite food.
They possess a remarkable capacity for remembering the exact time when they are likely to receive a large quantity of eatables from on board. Every day, about noon, the vicinity of the ship became animated, and towards one o'clock, after the crew had finished dinner, these lively creatures were close behind, and even fought for the pieces of tow with which the coppers had been cleansed. The boldest amongst them was the Cape pigeon, which pounced, with the utmost avidity, upon the dainty morsels thrown overboard, raising a loud scream, swimming round its prey, diving for sinking fragments, or snatching from each other those they had secured. Then came the black and brown-spotted and white albatrosses. As soon as one of these colossal birds appeared on the scene of strife, the uproar of the screaming pigeons at once became still; they kept themselves at a respectful distance from the voracious albatross, which quietly consumed its lion's share. In a few moments, yet greater numbers of these assembled, of which the black ones (Phœbetria fuliginosa), like the large petrels, are extremely shy, and rarely approach the ship within gun-shot. The other large-sized petrels acted similarly, the brown spectacled-petrel, so named from two singular-looking black rings round the eyes, being the most numerous. Along with these were several small Mother Carey's Chickens, and flights of other winged creatures swarming over the sea. The darker the sky, the more agitated the sea, the more actively do the Cape pigeons tumble and toss behind the ship; it appears that in rough stormy weather they see less distinctly and find food with difficulty, in consequence of which they are in a famished state. Only under these circumstances, and when the ship is moving slowly, can they be caught with a line. To angle for birds may appear rather odd to the reader, and yet it is common enough in the Southern Ocean, amusing the sailor, and providing the zoologist with means of obtaining these birds alive. For this purpose, however, circumstances must be comparatively favourable; that is to say, the weather must be rough, the sea agitated, and the ship making but little headway. When the sky is serene, and the sea calm, even the Cape pigeons do not think it worth their while to throw a glance at the bait; and if the ship is moving fast, they have not speed enough to catch it, because they only swim, and the ship outspeeds them. The line, moreover, must be of tolerable length, so as, in the event of any bird evincing a desire to snap, to allow as much to be paid out as is necessary to leave the bait precisely in the same spot, without towing it through the water. It sometimes also occurs, particularly after sunset, that these birds, continually following in the wake of the ship, do not see the line, strike against it, and entangle themselves so that they may be easily drawn on board. The scream of the storm-pigeon when caught, makes it betray its fate even before those on board have an idea that it has been captured.
For the albatross, it is of course necessary to use a stronger hook, which it is best to attach to a copper wire, because this being thinner than line, is not so readily perceived. In order that the whole apparatus may swim on the surface of the water, a few cork floats are also made fast.
When an albatross has hooked itself, the full strength of a man is requisite to draw it on board, for the bird, in its despair, dives and keeps its wings spread under water, so that the resistance is very considerable, and frequently even the strongest lines are broken. This cannot be wondered at when their size is considered, as they measure from 10 to 14 feet across the extended wings, while their weight amounts to from 10 to 18 lbs.