18 ENGLAND TO RIO DE JANEIRO CHAP. I 
described. It was about as large as the common kind, but 
differed from it in being whiter, especially about the face. 
We named it Procellaria crepidata, as its feet were like 
those of the gulls shot last week, black on the outside, but 
white near the legs. A large shoal of fish were all this 
day under the ship’s stern, playing about, but refusing to 
take bait. We contrived to take one of them with a fizgig: 
it was in make and appearance like a carp, weighing nearly 
two pounds. Its sides were ornamented with narrow lines, 
and its fins almost entirely covered with scales: called it 
Cheetodon cyprinaceus. 
16th. I had the opportunity of seeing a phenomenon I 
had never before met with, a lunar rainbow which appeared 
about ten o'clock, very faint, and almost or quite without 
colour, so that it could be traced by little more than an 
appearance resembling shade on a cloud. 
18th. This evening, trying, as I have often (foolishly no 
doubt) done, to exercise myself by playing tricks with two 
ropes in the cabin, I got a fall which hurt me a good deal, 
and alarmed me the more as the blow was on my head, and 
two hours after it I was taken with sickness at my stomach, 
which made me fear some ill consequence. 
19th. To-day, thank God, I was much better, and eased 
of all apprehensions. 
21st. To-day the cat killed our bird, Motacilla avida, which 
had lived with us ever since the 29th September entirely on 
the flies which it caught for itself: it was hearty and in 
high health, so that it might have lived a great while longer 
had fate been more kind. 
25th. This morning about eight o’clock we crossed the 
equinoctial line in about 33° W. from Greenwich, at the 
rate of four knots, which our seamen said was uncommonly 
good, the thermometer standing at 79°. (The thermometers 
used in this voyage are two of Mr. Bird’s making, after 
Fahrenheit’s scale, and seldom differ by more than a degree 
from each other, and that only when they are as high as 
80°, in which case the mean reading of the two instruments 
is set down.) This evening the ceremony of ducking the 
