96 R I O N E G R O. 
remained six to eight degrees colder until the 23d, when it again rose 
to the height it had been before. 
I have little doubt but this remarkable change and fall of tempera- 
ture were caused by the near approach to icebergs, some of which 
have been at times seen nearly in this latitude, 38° 55' S., longitude 
54° 30' W. After this we had line pleasant weather until our arrival 
off Rio Negro, the temperature of the air and water having fallen 
10° during our progress from Rio. 
On the 22d we experienced a heavy dew. Our observations 
confirmed the remarks of Captain King, that it is accompanied by a 
northerly wind or change to that quarter. 
We next passed over the position assigned the Ariel Rocks on the 
charts, and sailed two degrees on their parallel, but saw no indication 
of them. 
In approaching the coast, the soundings were remarkably regular, 
decreasing about a fathom in three miles. After passing to the south 
of the river La Plata, they were composed of fine gray sand, with 
pebbles and shells, while to the north they were of blue mud. 
Soundings were had in fifty fathoms water, one hundred and fifty 
miles off the coast. 
On the 25th we discovered the coast, which is a line of low sand- 
hills, without trees, and it exhibits little appearance of vegetation. 
In the evening we anchored off the bar, in eight fathoms water, just 
after which we experienced one of the remarkable squalls of this 
coast, that rose from the southward and westward ; it was attended 
with much lightning and thunder; quantities of sand and insects 
were blown off from the land. But little rain fell. The barometer 
indicated this squall by a depression of two-tenths of an inch. The 
wind soon changed and brought fine weather, the thermometer falling 
6° during the chancre. 
Having been led to believe we should be boarded by pilots on our 
anchoring off the bar, I was a good deal surprised to find none, and 
no endeavour making to board us, although the sea was quite smooth. 
The only appearances of inhabitants which we could see with our 
telescopes, were a few horsemen, suspiciously reconnoitring us from 
the flag-staff on the top of the hill. I then concluded to despatch the 
Sea-Gull under Lieutenant-Commandant Ringgold into the river, 
for the purpose of having communication with the town, directing 
him to take the channel leading to the northward and westward, 
as shown by the only chart we had, whilst I followed in the Flying- 
