On May 1, 1769, Captain Cook declared Fort Venus secure enough to bring the Endeavour’s most valuable cargo ashore Tahiti – an astronomical quadrant from the acclaimed mathematical instrument maker John Bird.
A quadrant measures the latitude of celestial objects while on land and was one of the key pieces of equipment the astronomer Charles Green needed to observe the transit of Venus that was due to take place on June 3. This was the reason for Cook’s voyage to the island.
Used in combination with an astronomical clock, the quadrant was also vital in confirming local time and helping establish longitude – that all-important metric still contested by scientists of the time.
The British explorers had already become acquainted with the Tahitians’ propensity for stealing and so bringing the quadrant on land was a major moment. But with Cook satisfied that Fort Venus would keep out any unwanted visitors, the specially made observatory tent was erected and Bird’s priceless device was brought ashore.
“This afternoon we set up the Observatory and took the Astronomical Quadrant ashore for the first time, together with some other Instruments, the fort being now finished and made as Tenantable as the time, Nature, and situation of the Ground and Materials we had to work upon would admit of,” wrote Cook.
He went on to describe the layout and security features of Fort Venus including a pair of canons at the ready.
“The North and South parts consisted of a Bank of Earth 4 1/2 feet high on the inside, and a Ditch without, 10 feet broad and 6 feet deep; on the West side facing the Bay a Bank of Earth 4 feet high, and Palisades upon that, but no Ditch, the works being at high-water mark. On the East side upon the Bank of the river was placed a double row of Casks, and, as this was the weakest side, the 2 four Pounders were planted there, and the whole was defended, beside these 2 Guns, with 6 Swivels, and generally about 45 Men with small Arms, including the Officers and Gentlemen who resided ashore. I now thought myself perfectly secure from anything these people would attempt.”
Unfortunately for Cook, the Tahitians were rather more expert in the art of pilfering than he gave them credit for. Having left the quadrant in its box in his own tent within Fort Venus overnight, when he and Green went to check on it next morning they were shocked to find that it was gone.
“This morning, about 9 o’clock, when Mr. Green and I went to set up the Quadrant, it was not to be found. It had never been taken out of the Packing Case (which was about 18 Inches square) since it came from Mr. Bird, the Maker; and the whole was pretty heavy, so that it was a matter of Astonishment to us all how it could be taken away, as a Centinal stood the whole night within 5 Yards of the door of the Tent.”
Once Green’s heart had started beating again he set off together with the naturalist Joseph Banks in search of the instrument, having been tipped off by the Tahitian chief they called Toobouratomita or Tubourai that it had indeed been stolen by a local. It took them the best part of the day and many miles but they eventually retrieved the quadrant, though not without relations becoming strained along the way. While Cook set out with others to find Banks and Green, the second lieutenant Zachary Hicks went against the captain’s orders and took the Tahitian chief they called Tootaha hostage.
“The Scene between Toobouratomita and Tootaha, when the former came into the Fort and found the latter in Custody, was really moving. They wept over each other for some time. As for Tootaha, he was so far prepossessed with the thought that he was to be kill’d that he could not be made sencible to the Contrary till he was carried out of the Fort to the people, many of whom Expressed their joy by embracing him; and, after all, he would not go away until he had given us two Hogs, notwithstanding we did all in our power to hinder him, for it is very certain that the Treatment he had meet with from us did not merit such a reward,” wrote Cook.
Green checked over the instrument and was relieved to find it mostly intact. Herman Spöring, Banks’ clerk and assistant, who also happened to be a trained watchmaker, was able to repair what damage there was. The astronomer’s thoughts returned to the transit of Venus while Cook reconsidered fort security.