UNITED STATES EXPLORING EXPEDITION. 



221 



OBSERVATORY. 

 TUTUILA. 



INSTRUMENTS USED ON SHORE. 



Standard barometer. 



Attached thermometer. 



Thermometer, with its bulb covered with black wool. 



Thermometer, lamp-black. 



Thermometer, " white wool. 



Thermometer, uncovered. 



Thermometer four feet below the surface. 



Hygrometer. 



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



56 



