[ 57 °] 
But if the diftance computed differs from the di- 
flance inferred from the obfervation, it muff be found 
by proportion from the Moon's horary motion to or 
from the ftar, how long time fhe will take to run 
over that difference ; whence the time will be found 
at Greenwich, when the true diftance of the Moon 
from the ftar was the fame with that refulting from the 
obfervation 5 which, compared with the time of the 
obfervation by the meridian of the fhip, gives the dif- 
ference of longitude from Greenwich, as before. If 
the diftance of the Moon from the ftar computed 
agrees with that refulting from obfervation within i o' 
or i2 r , and the diftance of the Moon from the ftar 
be not lefs than 20° or 30°, the horary motion of the 
Moon in the ecliptic may be taken for the horary 
motion of the Moon to or from the ftar ; but other- 
wife, the Moon’s longitude and latitude muft be found 
at an hour’s interval after the time aftumed at Green- 
wich, by adding the horary motions to the longitude 
and latitude computed ; and by the application of the 
rules, the diftance of the ftar from the Moon muft be 
found again at the end of that hour; which gives the 
horary motion to or from the ftar, as required. 
It is to be obferved, that the longitude thus found, 
is that of the fhip, at the inftant when the altitude of 
-the Sun or ftar was taken, by which the watch was 
regulated, and not at the time of the obfervation of 
the diftance of the ftar from the Moon ; for the watch 
being fuppofed not to vary conftderably during that 
interval of time, muft continue, to indicate the time 
according to the meridian, by which it was corrected ; 
and the obfervation of the diftance of the Moon from 
the ftar fhe wing the time at Greenwich, the difference 
muff: 
