UNITED STATES EXPLORING EXPEDITION. 



107 



OBSERVATORY. 

 ORANGE HARBOUR, TIERRA DEL FUEGO. 



INSTRUMENTS USED ON SHORE. 



Standard barometer. 



Attached thermometer. 



Thermometer exposed to the rays of the sun, the bulb being covered with black wool ; one foot and a 

 half from the ground. 



Thermometer, in the same situation, with bulb uncovered. 



These two thermometers were removed to the house during the night, and while the gales of wind lasted. 



Thermometer in the house or Observatory. 



Thermometer in a hole two feet and a half below the surface. 



Photometer, which generally stood at 12 in the Observatory ; the observations recorded are those made 

 when the weather admitted its being exposed in the open air. 



Hygrometer. 



Temperature of water, and at mast-head, observed on board U. S. Ship Vincennes. 



