The measurement in England was extended to a survey of the
whole kingdom; and the accurate maps thus obtained have been since
published. Arcs of the meridian have also been measured lately from Dunkirk
to Barcelona, - in Lapland, by which an error in the former measurement
there was corrected; - and in India.
We have been thus particular in our notice of this subject, because it is
evident that such measurements must lie at the foundation of all real
improvements in the construction of maps.
Let us next turn our attention to the improvements in navigation which have
taken place during the last and present centuries; these seem to consist,
principally, in those which are derived from physical science, and those
which are derived from other sources.
The grand objects of a navigator are the accurate knowledge of where he
exactly is, in any part of his course, and how he ought to steer, in order
to reach his destination in the shortest time. The means of ascertaining
his latitude and longitude, of calculating how far he has sailed, and at
what rate he is sailing, and the direction of his course with reference to
the port to which he is desirous to proceed, are what he principally
requires.
