What is the importance of the Queen Charlotte in the novel, Hornblower and the Atropos?

The Queen Charlotte is a canal boat upon which Hornblower takes passage to London. She runs through a series of locked canals and a two-mile tunnel cut through the Cotwolds. Queen Charlotte is seventy feet in length and five in beam, and draws less than one foot. She travels around nine miles per hour and is crewed by a single man at the tiller. As a towed craft, she is harnessed to a team of horses which provide propulsion both with and against any current. Queen Charlotte and her operation are discussed in the first two chapters of the novel.