“That branch of natural knowledge which may be called _nautical astronomy_, was undoubtedly in its infancy, when these voyages were first undertaken. Both instruments and observers, which deserved the name, were very rare; and so late as the year 1770, it was found necessary, in the appendix to _Meyer’s Tables_, published by the Board of Longitude, to state facts, in contradiction to the assertions of so celebrated an astronomer as the Abbé de la Caille, that the altitude of the sun at noon, the easiest and most simple of all observations, could not be taken with certainty to a less quantity than five, six, seven, or even eight minutes.[60] But those who will give themselves the trouble to look into the _astronomical observations_ made in Captain Cook’s last voyage, will find, that there were few, even of the petty officers, who could not observe the distance of the moon from the sun, or a star, the most delicate of all observations, with sufficient accuracy. It may be added, that the method of making and computing observations for finding the variation of the compass, is better known, and more frequently practised by those who have been on these voyages, than by most others. Nor is there, perhaps, a person who ranks as an officer, and has been concerned in them, who would not, whatever his real skill may be, feel ashamed to have it thought that he did not know how to observe for, and compute the time at sea; though, but a short while before these voyages were set on foot, such a thing was scarcely ever heard of amongst seamen; and even first-rate astronomers doubted the possibility of doing it with sufficient exactness.[61] “The number of places, at which the rise and times of flowing of tides have been observed, in these voyages, is very great; and hence an important article of useful knowledge is afforded. In these observations, some very curious and even unexpected circumstances have offered themselves to our consideration. It will be sufficient to instance the exceedingly small height to which the tide rises in the middle of the great Pacific Ocean; where it falls short, two-thirds at least, of what might have been expected from theory and calculation. “The direction and force of currents at sea make also an important object. These voyages will be found to contain much useful information on this head; as well relating to seas nearer home, and which, in consequence, are navigated every day, as to those which are more remote, but where, notwithstanding, the knowledge of these things may be of great service to those who are destined to navigate them hereafter. To this head also we may refer the great number of experiments which have been made for enquiring into the depth of the sea, its temperature, and saltness at different depths, and in a variety of places and climates.