Green had accompanied Mr. Maskelyne, afterwards Astronomer Royal, to Barbados in 1763 in H.M.S. Princess Louisa, in order to test Harrison's timekeeper, and also a complicated chair, from which it was supposed observations of Jupiter's satellites could be observed on board ship; and as this trial afforded the final triumph of the new method, one would have thought that on a voyage of circumnavigation he would have made every effort to get one of these watches.
Be this as it may, the Endeavour had no chronometer, and lunars were the mainstay of the expedition.
In these observations Green was indefatigable. Cook, an excellent observer himself frequently took part in them; but it was Green's especial business, and no doubt to him is due the major part of the determinations of accurate longitude, which is one of the very remarkable points of this voyage.
Green's log, which is extant, is filled with lunar observations, and the extraordinary coincidence between different observations attests the care with which they were made. I dwell upon this because, while full of admiration for Cook's knowledge, and his untiring zeal in every detail of his expedition, it is evident, from a study of the original documents, that without Green many opportunities of getting longitude would have been lost, Cook having no time to spare to make use of them. Let us give honour to whom honour is due.
The final results of the observations are not equally good, but this arises from the errors, before referred to, in the moon's place in the heavens as given in the almanac, which would vary with her position, and affect the longitude accordingly. The astonishing thing is, not that some longitudes are considerably in error, but that the majority of them are so near the truth.
The Endeavour sailed from the Thames on June 30th, 1768, and was in Plymouth Sound from July 14th to the 26th, when she finally sailed, Banks and the scientific staff having joined here.
She carried a complement, all told, of ninety-four, and very close stowage it must have been.
A list is given in this book, immediately before the "Journal," of every person on board when the ship sailed from Plymouth.
The draught of the ship was 13 feet 6 inches, and her provisions were calculated to last eighteen months. The original intention had been that the transit of Venus should be observed at the Marquesas; but the Dolphin's return before Cook sailed, with the news of the discovery of Tahiti and its friendly inhabitants, caused this island to be finally selected.
The exact text of Cook's orders cannot be given. They were secret orders; but, curiously enough, while the covering letter, which enjoined him to show them to nobody, which is dated July 30th, 1768, is duly entered in Admiralty Records, the orders themselves, which should follow in the letter book, are omitted. They have never been published. Nevertheless, we can gather what they were.