Suddenly these burst into flames.

They were the fire ships, which Vaudreuil had sent down to destroy the fleet.

They were filled with pitch, tar, and all sorts of combustibles, with shell and grenades mixed up with them, while on their decks were a number of cannon, crammed to the mouth with grapeshot and musketballs.
Fortunately for the English, the French naval officer in command lost his nerve, and set fire to his ship half an hour too soon; the other captains following his example.

This gave the English time to recover from the first feeling of consternation at seeing the fire ships, each a pillar of flame, advancing with tremendous explosion and noise against them.

The troops at once got under arms, lest the French should attack them, while the vessels lowered their boats, and the sailors rowed up to meet the fire ships.