In chapter 13, Jerome admits openly that
I do hate steam-launches; I suppose every rowing man does.
Jerome thus sets up an opposition between two modes of travel: the older-fashioned rowing boat and the modern steamboat, which of course is faster and more efficient. Jerome feels that the greater power of steamboats makes their users more arrogant, and indeed quite aggressive on the river; and the small rowing-boats, like Jerome’s own, are always obliged to get out of their way. Jerome resents this.
Jerome, George and Harris refuse to give way to steam launches in their path, however, and instead pretend not to notice them. In this way they manage to cause the steam-launches a lot of annoyance –which is exactly what they are aiming for.
It might appear that Jerome views steamboats as an undesirable modern intrusion on the old, leisurely life on the river. However, he displays quite another attitude in a later chapter when the three friends’ boat is towed up the river by a steam launch for a time, thus saving them some hard work. Now he lambasts the ‘wretched small boats’ (chapter 16) that hamper the passage of the steam launch. Therefore Jerome’s earlier diatribe against steam-launches is not really meant to be taken very seriously.