UNITED STATES EXPLORING EXPEDITION. 



203 



U. S. SHIP VINCENNES. 

 MATAVAI BAY, TAHITI. 



OBSERVATORY, POINT VENUS, TAHITI. 



INSTRUMENTS USED ON SHORE. 



Barometer (standard). 



Thermometer attached. 



Thermometer 2J feet from soil, with north-and-south exposure. 



Thermometer, the bulb being covered with white wool, in same position. 



lampblack, 



black wool, 



Thermometer in a hole four feet below the surface. 

 Hygrometer (Daniell's). 



The temperature of water, and the thermometer at mast-head, were registered on board tin- I'. S. Ship 

 Vincennes. 



