The answer is: irony.
Irony refers to meaning the opposite of what is being said. In the excerpt from "The Danger of Lying in Bed," the author Mark Twain makes use of irony to introduce a new outlook as regards traveling. In that respect, he suggests that staying at home is more dangerous than traveling by train. Thus, he overturns the common assumption that home is considered safe and traveling is viewed as hazardous.
