26 



REPORT ON 



Double Altitudes of the Sun for Time, observed at La Play a, San Diego Bay, California, 



June \%th, 1866. 



i6 m 41 s . 





112° 30' 



17 16 



'5 



17 5i-5 









19 10 





112 30 



19 46 





IS 



20 21.5 









Ex. ther. 



7i° 



Refraction 



— — 37"-4 



Parallax 





= + 4-7 



Index correction. 



[2O 

 f 2 



At. ther. 



359° 



11' 



3°" 



35 



20 



o° 



14' 



5o" 

 3° 



• 5° 



359 



11 



28.3 







14 



43-3 



Correction = 4- 16' 54". 2 



72° Bar. 30.12 inches. 



Sun's declination + 23 20' 22" 

 Latitude +32 41 58 



112 



Mean of observed double altitudes 

 Local apparent time . 

 Equation of time 

 Local mean time 

 Mean of chronometer times 

 Chronometer fast of local mean time 

 Longitude west .... 

 Chronometer slow of Greenwich mean time 



Double Altitudes of the Sun for Time, observed on Yerba Buena Island, San Francisco Bay, 

 California, June 26th, 1866. 



2 



15 



.0 



2 h 



2 7 m 



47 s -3 









"■•3 



2 



27 



58.6 



5 



18 



3 11 



2 



5° 



3 2 -5 



7 

 4 



48 

 58 



52.6 

 20.1 



40 s . 5 



18 



55-5 



18.5 



54-5 



3° 



75 



15 

 3° 



45 

 15 

 3° 

 45 



Index correction. 



2Q 



2O 



359° 



11' 



3°" 



35 



25 



o° 



14' 



3° 



5° 



.5° 



359 



11 



30.0 







14 



43-3 



Ex. ther. 67 

 Refraction = — 72". 5 

 Parallax = -f 6.6 



At. ther. 



Correction = 4- 16' 5 3". 4 



Bar. 

 Sun's declination + 23 22" 7" 

 Latitude 4- 37 48 46 



Mean of observed double altitudes 

 Local apparent time . 

 Equation of time 

 Local mean time 

 Mean of chronometer times 

 Chronometer fast of local mean time 

 Longitude west .... 

 Chronometer fast of Greenwich mean time 



75 3° ° 



+ 



5 8 s - 4 

 29.6 

 28.0 

 36.2 

 8.2 

 22.6 

 45- 6 



The chronometer used in making this observation was T. S. and J. D. Negus' No. 1287. 



True bearings were determined by measuring with, a sextant the angle between 

 the sun's limb and some well-defined terrestrial object, the time being noted at 

 the instant the angle was observed. If the terrestrial object was much elevated 

 above the horizon its angular altitude was also measured. Knowing the latitude 

 of the place of observation, the local time, and the sun's declination, the sun's 

 zenith distance and true bearing were calculated. Then, having the zenith dis- 

 tance of the sun, the zenith distance of the terrestrial object, and the measured 

 angle between the sun and the terrestrial object, the horizontal angle between them 



