RIO NEGRO. 109 



It was my intention to pass within or to the north of the Hermit 

 Islands into Nassau Bay, but the wind did not permit our doing so. 

 This bay forms a large indenture in the southern coast of Terra del 

 Fuego, a few miles to the northward of Cape Horn ; it is about thirty 

 miles east and west, by eight miles north and south, and is somewhat 

 protected from the heavy seas by the Hermit Islands. Around the bay 

 are found some harbours sheltered by small islands, and surrounded by 

 precipitous rocky shores, with occasionally a small 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. 



PARHELION. 



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 op- 

 position. 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 dif- 

 ference of five degrees 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 



