o/i the Variation and Dip of the Needle. 255 



is above the horizontal line ; and, consequently, that the ob- 

 servation is made to the south of the magnetic equator. 



The declination of the needle was observed on shore by 

 means of a small compass, with a telescope, which had been 

 previously employed in hydrographical voyages by M. Gautier, 

 Captain of the Coquille. 



When the azimuth of a terrestrial object had been deter- 

 mined by numerous observations taken with a geodetic circle, the 

 object was observed with the compasses above mentioned, and 

 the definitive declination was that which resulted from the read- 

 ings taken at the two extremities of the needle, before and af- 

 ter the return of the instrument, and before and after the re- 

 versing of the needle in its case. 



The magnetic power of the Coquille was measured with 

 every possible accuracy, and presented nothing that was re- 

 markable. 



Before the expedition sailed the dip was observed at Tou- 

 lon in June 1822. 



Lat. 43° r 9". Long. 6° 0' 41". Mean Dip. 63° 57' 9" 



The following observations were made in the voyage from 

 Toulon to St Catherine's, in Brazil, in August, September, 

 and October 1822. 



