PREFACE. v 
but at the same time least certain data in hydrography ; the man of 
science therefore requires something more than the general result 
of observations before giving his unqualified assent to their accuracy, 
and the progress of knowledge has of late been such, that a com- 
mander now wishes to know the foundation upon which he is to 
rest his confidence and the safety of his ship ; to comply with this 
laudable desire, the particular results of the observations by which 
the most important points on each coast are fixed in longitude, as 
also the means used to obtain them, are given at the end of the 
volume wherein that coast is described, as being there of most easy 
reference. 
The deviations in the Atlas from former practice, or rather the 
additional marks used, are intended to make the charts contain as 
full a journal of the voyage as can be conveyed in this form ; a 
chart is the seaman's great, and often sole guide, and if the infor- 
mation in it can be rendered more complete without introducing 
confusion, the advantage will be admitted by those who are not 
opposers of all improvement. In closely following a track laid 
down upon a chart, seamen often run at night, unsuspicious of 
danger if none be marked; but some parts of that track were 
run in the night also, and there may consequently be rocks or 
shoals, as near even as half a mile, which might prove fatal to them ; 
it therefore seems proper that night tracks should be distinguished 
from those of the day, and they are so in this Atlas, I believe, for 
the first time. A distinction is made between the situations at noon 
where the latitude was observed, and those in which none could be 
obtained ; and the positions fixed in longitude by the time keepers 
are also marked in the track, as are the few points where a latitude 
was obtained from the moon. 
It has appeared to me, that to show the direction and strength of 
the winds, with the kind of weather we had when running along 
