Cook was a man of great ambition and curiousity. He worked hard in his job aboard ships that carried coal to English ports, and soon got his mate's certificate. He would probably have got a job as skipper, except war broke out, and he decided to join the British Navy.

He was sent out to America, where he worked so well that before long he found himself master of a king's ship, the Mercury. He was sent to join Admiral Saunders who was besieging Quebec in Canada. There he was given the difficult and dangerous work of charting the channel of the St. Lawrence right up to the French lines, and he did an excellent job. He worked at night in danger of his life, On one occasion Indians leapt on to the stern of his boat as he jumped off the bows - but the work was done, and found to be absolutely reliable. His charts contributed to the British capture of the French city of Quebec later on that year.

How he found time, or got hold of the necessary books, to make himself an expert surveyor and cartographer, and to study mathematics and astronomy, is a mystery. But even though he had never been to university he taught himself to be an expert in these subjects. He even wrote scientific papers on complicated mathematical problems such as finding out where you are by using the moon.