by Oceans of two Altitudes of the Sun. i 
REMARKS. 
1 . All the altitudes that are taken on the same side of noon, 
tend only to correct the error which may be supposed to exist 
in the greatest of these altitudes, and can have no effect in 
removing any inaccuracy to which the greatest altitude on the 
other side of the meridian may be subject. Hence we must 
take more than one altitude on each side of noon, if we are 
desirous of obtaining a very exact conclusion. 
2. When some of the observations are made in the morn- 
ing, and others in the afternoon, the smaller the hour-angle, in 
every instance, the more favourable it will be for our purpose. 
But, if we cannot procure an altitude on each side of the meri- 
dian, we ought to make one observation when the hour-angle 
is as large as possible, and with this all the rest should be se- 
parately combined. We must be cautious, however, not to let 
the sun be too near the horizon, lest the apparent altitude 
should be affected by the uncertainty of the refraction. 
3. If the clock were to furnish us with the true time, we 
might combine together any two observations made within the 
proper limits, without applying to the first table, and deduce a 
very exact correction. Should there even be a small error in 
the supposed time, we might still proceed in the same manner, 
without being liable to any material inaccuracy, provided the 
difference betwixt the hour-angles was not very considerable. 
The error, indeed, occasioned by adopting this method of find- 
ing the two areas, and taking a mean betwixt them for the 
value of gb , may easily be determined in any particular case. 
If t and t' be the respective tangents of the smaller and greater 
hour-angles, and i their difference ; z the error of the clock in 
MDCCXCIX. Q 
