Captain Owen on Circummeridian Altitudes. 165 
lowing azimuthal bearings of the sun’s east and west limbs, and 
altitudes of his upper and lower limbs. 
Note these observations in the form following, or some such 
form, viz.: 
At D1. 20th May, 1844, Theodolite Zero 360°.00.0 North Magnetic. 
Bearing or Azimuth. Altitudes. 
Zero 00°.00/.0 North end of magnet. These observations must be made at the centre 
O “ « € 16 altitude © “o« /« wire of the telescope, and repeated as often as re- 
re “a & EO @« « « quired; each observation to be separately noted. 
If the variation of the needle be known, then the direction of 
the true meridian is known, or taking the observations at equal 
intervals of 30’ or 1° of azimuth, and noting the changes of the 
successive altitudes, the precise azimuth of equal altitudes rising 
and falling may be elicited, which note thus, under the observa- 
tions, being the mean of azimuths to equal altitudes. 
Zero, 000°.00!.0 North magnetic. 
“« «Apparent south meridian. 
1. Collect into one column the differences of the apparent 
meridian azimuth, and each of the other azimuths observed, and, 
in another column, all the altitudes observed, and mean the latter. 
Carry out, into other columns, first, the azimuthal differences from 
the apparent meridian noted in degrees and tenths only, and, 
second, the squares of these quantities. 
2. Sum the squares, and mean them by the number of obser- 
vations, which call Q. 
3. Let the motion of sun in one degree of azimuth from the 
meridian —a be either calculated, or taken from a prepared table. 
The form for calculation is the following: 
Latitude, 44° 26/ log. cosine, 9.854 60)9.863 =a” 
Declination, 20 6 log. secant, 0.027 ~ 0 1644—a! 
Zen. Dist. 24 20 log.sine, 9.615 
Constant, 31.4144 log. 1.49754 
a=9".863 log. 0.994 
