Himatava Movunrains. 363 
WAY BoE 12, 
Conrarns the logarithmic factor, for finding the difference of Azimuth 
of the two ends of a perpendicular arc. 
EXAMPLE.” 
Ler the length of a perpendicular to the meridian be 375,000 feet, 
and the latitude of the right angle 31 07: Required the difference of 
Azimuth of its two extremities? 
Log. of 375,000 5% 
Factor to 31 07 rf 
Difference of Azimuth required 99°30 = 3:3483 
Ir this difference were greater it might be necessary to correct it by 
Table il, as in the case of the longitude, but unless the correction 
amounted to a few seconds it is hardly worth attending to, particularly as 
Azimuths are not easy to be observed with great precision. 
Ir is to be noted, that though these two tables give the correct dif- 
ference of Azimuth of the two ends of the perpendicular, yet that this is 
not always the difference answering to the two ends of the corresponding 
oblique arc, because it is evident, that where the arcs are large there will _ 
be a considerable spherical excess, and this must be taken into considera- 
tion always. 
VOL. XIV. Se A Tie: 
