UNITED STATES EXPLORING EXPEDITION. 



233 



OBSERVATORY. 

 APIA, ISLAND OF UPOLU. 



INSTRUMENTS USED ON SHORE. 



Standard barometer. 

 Attached thermometer. 



Thermometer, the bulb covered with black wool. 

 " " white wool. 



" lampblack, 



uncovered. 

 Hygrometer. 

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



