26 GEOGRAPHIC TABLES AND FORMULAS. [bull. 234. 
Example. 
June 20, 1903. h. m. s. 
Watch time of sun's transit 11 50 25 
Equation of time -f-1 04 
Local mean noon 11 51 29 
Or watch slow 8 31 
The error of observation should not exceed two or three seconds 
and the error resulting from incorrect meridian will be approximately 
four seconds for each 1' error in meridian. 
Applications of Tables 1 and 3. 
1. Required the hour angle and azimuth of Polaris, for a station in latitude 46° 
N., longitude 90° W., at 8'^ 24"^ p. in., November 7, 1910, 
h. m. 
Astronomical time of observation, 1910, November 7 8 24. 
Equivalent to time of November 6 32 24. 
h. m. 
Astroii. time, U. C. Polaris, November 1 (table 1).. 10 45.3 
Reduction to November 6 « ( B ) , subtract ^19.7 
Astron. time, U. C. Polaris, Novembers , 10 25.6, subtract. clO 25.6 
Hour angle of Polaris, at observation 21 58. 4 
Subtract from '?23 56. 1 
Time argument for table 3 1 57. 7 
Azimuth of Polaris, at observation 0° 51^ E. 
2. Required the hour angle and azimuth of Polaris, for a station in latitude 41° 
12^ N., longitude 94° W., at 6'^ 16™ a. m., November 19, 1904. 
]i. m. 
Astronominal time of observation, 1904, November 18 18 16. 
h. 111. 
Astron. time, U. C. Polaris, November 15 (table 1).. 9 47. 1 
Reducti( )n to November 3 8, subtract 11.8 
Astron. time, U. C. Polaris, November 18 9 35. 3, subtract . 9 35. 3 
Hour angle of "Polaris, at observation, and time argument for tal)le 3 ^8 40. 7 
Azimuth of Polaris, at observation (table 3) , 72^ or /" 1° 12^ W. 
The follow^ing- four examples illustrate any difficulties in the use of 
tables 1 and 3: 
"By reference to the above table, the surveyor will observe that the times, between November 1 
and L5, are greater than 8'' 24™; consequently, the culmination for one day earlier, November 6, will 
be used. 
?>From table 1, opposite sixth day of month. 
« To subtract, take one day from November 7, and add its equivalent, 24'', to 8'' 24'", making, Novem- 
ber 6, 32i> 24™ (which is the time expressed by November 7, 8'' 24m) ; then subtract in the usual manner. 
'^'See last clause of footnote, page 24. 
cin case the hour angle comes out greater than ll^ 58™, subtract it from 23'' Bfi™.!; see example 4, 
above. 
/The hour angle being less than 11'' 58"i, the azimuth is west; see precepts, top of table 8. 
