Before the voyages of the present reign took place, nearly half the surface of the earth was hidden in obscurity and confusion.

From the discoveries of our navigator, geography has assumed a new face, and become, in a great measure, a new science; having attained to such a completion, as to leave only some less important parts of the globe to be explored by future voyagers.[17] [Footnote 17: Lieutenant Roberts's admirable chart will set this matter in the strongest light.] Happily for the advancement of knowledge, acquisitions cannot be obtained in any one branch, without leading to acquisitions in other branches, of equal, and perhaps of superior consequence.

New oceans cannot be traversed, or new countries visited, without presenting fresh objects of speculation and inquiry, and carrying the practice, as well as the theory, of philosophy to a higher degree of perfection.
_Nautical astronomy_, in particular, was in its infancy, when the late voyages were first undertaken; but, during the prosecution of them, and especially in Captain Cook's last expedition, even many of the petty officers could observe the distance of the moon from the sun, or a star, the most delicate of all observations, with sufficient accuracy.

As for the officers of superior rank, they would have felt themselves ashamed to have it thought that they did not know how to observe for, and compute the time at sea; though such a thing had, a little before, scarcely been heard of among seamen.

Nay, first-rate philosophers had doubted the possibility of doing it with the exactness that could be wished.