112 
RIO NEGRO. 
ravine forming a cove, into which streams of pure water discharge 
themselves, affording a safe and convenient landing-place for boats. 
On the morning of the 16th, on board the Porpoise, Lieutenant 
Dale observed a remarkable parhelion, of which he made the annexed 
sketch. 
The upper is the true sun, the lower the mock sun. They were of 
equal size, and nearly of the same brightness. The latter was about 
a diameter below the former. The sun's altitude was 8°. At the 
same altitude, and 21° 40' south of it, was another mock sun, showing 
prismatic colours towards the sun, and with a brush of light in 
opposition. No halo or arc was seen. The whole disappeared in 
about fifteen minutes. The masthead temperature was not noted 
on board the Porpoise; but according to that of the Vincennes, 
there was a difference of 5° in temperature at the time between 
the deck and the masthead, showing a state of atmosphere favourable 
to this phenomenon. Barometer 29-55 in., temperature 42°. 
In passing the cape the weather was delightful. We sailed within 
two miles of this dreaded promontory, and could not but admire its 
worn and weather-beaten sides, that have so long been invested with 
all the terrors that can beset sailors. Here we first encountered the 
long swell of the Pacific, but there was scarcely a ripple on its 
surface. Although the landscape was covered with snow,* the lowest 
temperature we had yet experienced was 40° Fahrenheit. 
The Porpoise, just before night, made signal that she wished to 
speak us, and sent on board a tub filled with a large medusa, for 
