observations for time and longitude. 
185 
distances should always be observed in sets, with stars east and west of 
the moon, and as nearly equidistant from it as possible; the observer 
should also note which limb of the moon has been observed, and whether 
the star was east or west of it. The more nearly the two bodies approach 
the same horizontal plane, the easier will be the observation to take, and 
distances between 45° and 90° will be least liable to errors in obser¬ 
vation. 
The thermometer and the barometer (or its equivalent, a boiling-point 
thermometer) should be noted, and the refraction corrected accordingly; 
because, if thermometric and barometric corrections be omitted, in 
observations made on a high and heated plateau, there may be serious 
errors in the results. 
A complete pair of lunars, made wholly by one person, consists of the 
following observations, in addition to those for latitude . 
An hour before beginning to observe, get everything in perfect order; 
see that the lamp is well trimmed, its air-holes free, and that it is filled 
with oil. Also rehearse the expected observations, that no hitch may 
occur after they have commenced. Then let the hand and eye have 
ample time to repose, and go on as follows 
1. Read thermometer and barometer. 
2. Observations for index error. 
3. Three altitudes for time, star e. 
4. Three altitudes for time, star w. 
*5. Three altitudes of moon. 
6. Five lunar distances, star e. of moon. 
7. Five lunar distances, star w. of moon. 
*8. Three altitudes of moon. 
*9. Three altitudes for time, star w. 
*10. Three altitudes for time, star e. 
It is not absolutely necessary to take the altitudes marked with an 
asterisk, as they can be computed as shown on p. 193. For this pur¬ 
pose, however, it is necessary that the latitude of the place, and the exact 
local time when the distances were observed, should be known. The 
time can be found in the manner shown on pp. 153-157. The observa¬ 
tion for time, the latitude of the place, and which limb of the moon was 
