A longboat is a type of ship's boat that was in use from circa 1500 or before. Though the Royal Navy replaced longboats with launches from 1780, examples can be found in merchant ships after that date. The longboat was usually the largest boat carried. In the early period of use, a ship's longboat was often so large that it could not be carried on board, and was instead towed. For instance, a survey of 1618 of Royal Navy ship's boats listed a 52 ft 4 in (16 m) longboat used by the First Rate Prince, a ship whose length of keel was 115 ft (35 m). This could lead to the longboat being lost in adverse weather. By the middle of the 17th century it became increasingly more common to carry the longboat on board, though not universally. In 1697 some British ships in chase of a French squadron cut adrift the longboats they were towing in an attempt to increase their speed and engage with the enemy.