Captain Owen on Circummeridian Altitudes. 18] 
alent to a change of declination; therefore the equation of the 
apex (¢) is the only and a constant equation of equal altitudes by 
which the middle time between such equal altitudes is to be re- 
duced to the meridian, within certain limits from the meridian, 
depending on the minute changes of d, the motion in declination, 
and of minute changes in the velocity of the vessel in latitude. 
The effect of a motion in declination on the least altitudes at 
the lower transit, is manifest; the lower apex is as much below 
the meridian altitude there, as the greatest altitude exceeds the 
meridian altitude, at the upper transit. 
I will forbear, at this time, to draw all the practical consequences 
from the foregoing development of this problem, which are deriv- 
able from it, although they are numerous, and some, I think, im- 
portant. 
