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 commander 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 information 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