bed
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 deg. 7' N. and longitude 28 deg. 50'.

On the 25th we crossed the Line with the usual ceremonies, in longitude
29 deg. 30', when, by the result of several very good azimuths, the
variation was 2 deg. 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 deg. 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.

In the evening of the 29th, we observed that luminous appearance of the
sea which has been so often mentioned by navigators, and of which such
various causes have been assigned; some supposing it to be occasioned by
fish, which agitated the water by darting at their prey, some by the
putrefaction of fish and other marine animals, some by electricity, and
others referring it to a great variety of different causes. It appeared
to emit flashes of light exactly resembling those of lightning, only not
so considerable, but they were so frequent that sometimes eight or ten
were visible almost at the same moment. We were of opinion that they
proceeded from some luminous animal, and upon throwing out the
casting-net our opinion was confirmed: It brought up a species of the
_Medusa_, which when it came on board had the appearance of metal
violently heated, and emitted a white light: With these animals were
taken some very small crabs, of three different species, each of which
gave as much light as a glow-worm, though the creature was not so large
by nine-tenths: Upon examination of these animals, Mr Banks had the
satisfaction to find that they were all entirely new.[70]

[Footnote 70: The reader is referred to the account of Captain
Krusenstern's circumnavigation, for a very satisfactory relation or an
experiment on this subject, which clearly proves the truth of the
opinion above stated, as to the cause of the shining appearance so often
noticed at sea. It is too l