[ 5 6 9 ] 
But in cafe of a ftar, it is neceifary to apply an- 
other rule alfo. Seven places of logarithms, be- 
fides the index, muft be ufed, in computing from 
this rule, and the calculation muft be carried to 
feconds. 
R U L E II. 
To the conftant logarithm 3-5363* add the fines 
of the Moon’s and ftar’s latitudes, the verfed-fine of 
the difference of longitude, and the co-fecant of the 
approximate diftance juft found j the fum, abating 40 
from the index, is the logarithm of a number of mi- 
nutes, to be fubtradted from the approximate diftance, 
to find the true diftance, if the latitudes of the Moon 
and ftar are of the fame denomination; but to be 
added, if they are of contrary denominations. The 
fecond of thefe two rules, though only an approxima- 
tion, is fo exadt, that if the latitude of the Moon was 
5 0 , and that of the ftar 1 5 0 , the error refulting would 
be only 10" in the diftance. Four places of figures 
will be fufficient in computing from this rule. 
If the diftance of the Moon from the ftar thus 
computed, at the affumed time under a known me- 
ridian, fuppofe Greenwich, agrees with the diftance 
obferved, corredted for refra&ion and parallax, the 
time at Greenwich was affumed right, and the dif- 
ference between this time and the time of the obfer- 
vation under the unknown meridian, is the difference 
of longitude in time between the faid meridian and 
Greenwich ; which is turned into degrees and mi- 
nutes of the equator, by allowing 1 5 0 for every hour, 
and i° for every four minutes of time. 
4D 2 But 
