my deductions, and almost the facts were distrusted; and in the first
construction of the charts I had feared to deviate much from the usual
practice. Application was now made to the Admiralty for experiments to be
tried with the compass on board different ships; and the results in five
cases being conformable to one of the three laws before deduced, which
alone was susceptible of proof in England, the whole were adopted without
reserve, and the variations and bearings taken throughout the voyage
underwent a systematic correction. From these causes the reconstruction
of the charts could not be commenced before 1813, which, when the extent
of them is considered, will explain why the publication did not take
place sooner; but it is hoped that the advantage in point of accuracy
will amply compensate the delay.

Besides correcting the lunar distances and the variations and bearings,
there are some other particulars, both in the account of the voyage and
in the Atlas, where the practice of former navigators has not been
strictly followed. Latitudes, longitudes, and bearings, so important to
the seaman and _un_interesting to the general reader, have hitherto been
interwoven in the text; they are here commonly separated from it, by
which the one will be enabled to find them more readily, and the other
perceive at a glance what may be passed. I heard it declared that a man
who published a quarto volume without an index ought to be set in the
pillory, and being unwilling to incur the full rigour of this sentence, a
running title has been affixed to all the pages; on one side is expressed
the country or coast, and on the opposite the particular part where the
ship is at anchor or which is the immediate subject of examination; this,
it is hoped, will answer the main purpose of an index, without swelling
the volumes. Longitude is one of the most essential, 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