During our course from Teneriffe to Bona Vista we saw great numbers of flying fish, which from the cabin-windows appear beautiful beyond imagination, their sides having the colour and brightness of burnished silver; when they are seen from the deck they do not appear to so much advantage, because their backs are of a dark colour. We also took a shark, which proved to be the Squalus Carcharias of Linnaeus.
Having lost the trade-wind on the 3d, in latitude 12°14', and longitude 22°10', the wind became somewhat variable, and we had light airs and calms by turns.
On the 7th, Mr Banks went out in the boat, and took what the seamen call a Portuguese man of war; it is the Holuthuria Physalis of Linnaeus, and a species of the Mollusca. It consisted of a small bladder about seven inches long, very much resembling the air-bladder of fishes, from the bottom of which descended a number of strings of a bright blue and red, some of them three or four feet in length, which upon being touched sting like a nettle, but with much more force. On the top of the bladder is a membrane which is used as a sail, and turned so as to receive the wind which way soever it blows: This membrane is marked in fine pink-coloured veins, and the animal is in every respect an object exquisitely curious and beautiful.
We also took several of the shell-fishes, or testaceous animals, which are always found floating upon the water, particularly the Helix Janthina and Violacea; they are about the size of a snail, and are supported upon the surface of the water by a small cluster of bubbles, which are filled with air, and consist of a tenacious slimy substance that will not easily part with its contents; the animal is oviparous, and these bubbles serve also as a nidus for its eggs. It is probable that it never goes down to the bottom, nor willingly approaches any shore; for the shell is exceedingly brittle, and that of few fresh-water snails is so thin: Every shell contains about a tea-spoonful of liquor, which it easily discharges upon being touched, and which is of the most beautiful red-purple that can be conceived. It dies linen cloth, and it may perhaps be worth enquiry, as the shell is certainly found in the Mediterranean, whether it be not the Purpura of the ancients.[69]
[Footnote 69: It is quite impossible to discuss this subject here. But it may be worth while to refer the learned reader for some curious information about it, to the illustrious Bochart's work entitled Hierozoicon, Part II. Book V. Ch. II. There are several sorts of sea-shells, that yield the purple-dye so much esteemed among the ancients. Pliny, who has written on the subject, divides them into two classes, the buccinum and purpura, of which the latter was most in request. According to him, the best kinds were found in the vicinity of Tyre. That city was famous for the manufacture of purple. To be Tyrio conspectus in ostro, seemed, in the estimation of the Mantuan poet, essential to his due appearance in honour of Augustus, Geor. 3--17. But several other places in the Mediterranean afforded this precious article. Thus Horace speaks of Spartan purple,
Nec Laconicas mihi
Trahunt honestae purpuras clientae.Od. Lib. 2. 18.
The English reader will be much pleased with several interesting remarks as to the purple and other colours known to the ancients, given in President Goguet's valuable work on the origin of laws, arts. &c. &c. of which a translation by Dr Henry was published at Edinburgh 1761.--E.]
Nec Laconicas mihi
Trahunt honestae purpuras clientae.
On the 8th, in latitude 8° 25' north, longitude 22° 4' west, we found a current setting to the southward, which, the next day in latitude 7° 58', longitude 22° 13', shifted to the N.N.W. 1/4 W. at the rate of one mile and a furlong an hour. The variation here, by the mean of several azimuths, appeared to be 8° 39' W.
On the 10th, Mr Banks shot the black-toed gull, not yet described according to Linnaeus's system; he gave it the name of Larus crepidatus: It is remarkable that the dung of this bird is of a lively red, somewhat like that of the liquor procured from the shells, only not so full; its principal food therefore is probably the Helix just mentioned. A current to the N.W. prevailed more or less till Monday the 24th, when we were in latitude 1° 7' N. and longitude 28° 50'.
On the 25th we crossed the Line with the usual ceremonies, in longitude 29° 30', when, by the result of several very good azimuths, the variation was 2° 24'.
On the 28th, at noon, being in the latitude of Ferdinand Noronha, and, by the mean of several observations by Mr Green and myself, in longitude 32° 5' 16" W. which is to the westward of it by some charts, and to the eastward by others, we expected to see the island, or some of the shoals that are laid down in the charts between it and the main, but we saw neither one nor the other.