18 



REPORT ON 



Double Altitudes of the Sun for Time, observed at Ceara, Brazil, December itf/i, 1865. 



ii' 



Index correction. 



2(3 



Ex. ther. 86 

 Refraction = 4s".6 

 Parallax = + 5.6 



Correction = + 16' 4o".o 



At. ther. 83 Bar. 30.00 inches. 



Sun's declination 23 15' 27".4 



Mean of observed double altitudes 

 Mean of chronometer times . 

 Equation of time 



99 

 n h 



5' o".o 

 S4 m 42'-6 



4 53-7 



Reducing this observation with latitude = 3 43' 15". we find the chronometer 

 2 h 26" 30'. 7 slow of local mean time. Reducing it with latitude 3 44' 15", 

 we find the chronometer 2 h 26 m 33". 1 slow of local mean time. 



In order to determine both the latitude of Ceara and the error of the chronometer 

 from the three observations which have just been given, we proceed as follows: 



Comparing the error obtained on the afternoon of December 13th, with that 

 obtained on the afternoon of December 14th, we find that the chronometer was 

 losing 1.17 seconds per day; and this rate is independent of any small change in 

 the adopted value of the latitude. 



By means of this rate, reducing all the observed chronometer errors to 2 h 26 m 

 P. M. December 14th, and then plotting them according to Sumner's method, we 

 get for the place of observation 



Latitude 3 43' 59" S. 

 ind for the chronometer, 



Chronometer slow of local mean time 2 11 26 32'.s 



Longitude west . . . 2 34 6 



Chronometer slow of Greenwich mean time . . . . 5 o 38.5 



Double Altitudes of the Sun for Time, observed at Pcrnambuco, Brazil, December 2$d, 1865. 



7" 30" '5' 

 3<> 39-5 

 3' 3 

 3* 52-5 

 33 '5 

 33 40 



118 



n.S 



Index correction. 



Ex. ther. 83 

 Refraction = 32". i 

 Parallax = + 4.5 



At. ther. 



Bar. 



Sun's declination 23 26' 31" 

 Latitude 8 3 37 



Mean of observed double altitudes 

 Local apparent time . 

 Equation of time 

 Local mean time 



1 1 8 20' 



io h 9" 



o 



10 8 



o".o 



3'-5 

 31.2 



32-3 



