C 77 ] 
hence (he may know herfelf to be at the place E, 
fomewhat more to the eaftward, than the fand flae 
wants to avoid, and at the diftance of almoft a mile 
from it. She may now therefore fafely change her 
courfe, and fland due fouth, till having brought the 
light C to bear weft by north ftae is right over-againft 
the extremity of the fand, at the diftance of about 
three or four hundred yards. If ftie ftill keeps the 
fame courfe about three hundred yards farther, the 
lights will then fubtend an angle of only 2° 30', when 
fhe will be fo far to the fouth, as to be clear of all 
danger, though flie fhould from thenceforward fteer 
due weft; but, for greater fecurity, we will fuppofe her 
ftill continuing to ftretch away a little more to the 
fouthward, by fleering fouth weft for about a quar- 
ter of a mile farther. From hence then fhe may keep 
near due weft, wnth which courfe the two lights, in 
a run of a mile and a quarter, or a little more, will 
both be brought to bear north weft, and be feen to- 
gether. In a run of about half a mile more, they 
will be again open on the contrary fide from the 
former to about 3°, from which they will open to 10°, 
in a paftiige of near half a mile farther, when the 
fhip will be arrived at the place G, the light C bear- 
ing then due north. The change of the angle being 
now very great in a very fmall diftance, it will be 
very eafy to keep the ftiip with great exadnefs to 
whatever part of the channel we pleafe. Let us how- 
ever fuppofe, that we mean to keep her in the courfe 
laid down in the chart ; from G then we muft fteer 
north weft a little weft, and in a run of about a mile, 
we fhall firft increafe the angle of the two lights, till 
it is fomewhat more than 20”, the light C tlien bear- 
