260 OBSERVATIONS OF THE ECLIPSE 



from the imperfections of the lunar tables, which appear to 

 give the moon's longitude at the time of the eclipse at least l' 

 too much : the error in latitude at the same time is almost in- 

 sensible. 



No. XLII. 



Observations of the eclipse of the sun, June 1 6th, 1806: made at 

 the Forest, near Natchez. — Latitude 31° 27' 48" N. and sup- 

 posed Longitude about 6 h 5' 25" to 40", W. of Greenwich, by 

 William Dunbar Esq. 



Read August !5th, 1806. 



IN these observations, an excellent clock with a gridiron 

 pendulum was used, made by J. Bullock of London ; a port- 

 able cbronometer served occasionally as a companion to the 

 clock, which last was frequently regulated and corrected, by 

 equal altitudes of the sun, taken by a circle of reflection. 



J April 28th, 1806, astronomical time. With a six-feet 

 Gregorian reflecting telescope, power 100, observed an occul- 

 tation of e Iconis by the moon, as follows: 



I e Si Immersion at 8" 49' 10-i", per clock. The emer- 

 sion was not seen; the star was at some distance from the 

 moon's limb, before it was noticed, which was ascribed to the 

 extreme brightness of the moon, then nearly on the meridian. 



The following new and short formula was used, for finding 

 the equation of equal altitudes, viz. To the logarithmic co- 

 sine of the latitude, add the sine of the half-interval, in de- 

 grees, and the arith. comp. of the cosine (or secant) of the 

 altitude; the sum, rejecting tens from the index, is the sine 

 of an angle : take out the corresponding cotangent, to 

 which add the arith. comp. of the cosine (or secant) of the 

 sun's declination, and the logarithm of the declination, gain- 

 ed or lost during the half-interval, reduced to seconds of 

 rime ; the sum, rejecting tens from the index, is the logarithm 

 of the correction or equation of equal altitudes, in seconds of 



