What was Captain James Cook's destination?

James Cook's original mission was to observe the transit of Venus from the vantage point of Tahiti.

Cook was then under secret orders to try to find the great unknown southern continent, and claim it for Britain. In so doing, he charted the eastern coastline of what he called "New South Wales" (now Australia), making extensive notes on the people, flora, fauna and prospective suitability for colonisation, and reported back to England.